Secondary Structural Components Research Articles

Effect of pH‐shifting treatment on the structural characteristics and nutritional quality of the ultrasonically extracted protein isolate from soybean meal

AbstractSoybean meal is an underutilized byproduct of the soybean oil processing industry, which is rich in high quality protein but mostly used as an animal feed. Valorization of soybean meal on a large scale is possible by extracting protein isolate and modifying its structural characteristics through pH‐shifting or ultrasonic treatment, which has a direct association with the better functional properties of protein isolate. The present study aimed to evaluate the impact of pH‐shifting treatment on the structural characteristics and nutritional quality of ultrasonically extracted soybean meal protein isolate (SMPI). The results showed that the pH shifted SMPI had higher hydrophobicity (60.5–104.3) and free sulfhydryl group (22.67–24.45 μmol/g) than without pH shifted SMPI (53.5 and 19.67 μmol/g, respectively). The fluorescence intensity of the SMPI treated at extreme acidic and alkaline pH was higher than that of other pH‐treated samples. The ꞵ‐sheet (39.68%) components of SMPI treated at pH 10 showed the highest value when compared to other pH‐treated (38.18–39.26%). The alkaline pH‐treated sample had higher concentration of essential amino acids (36.16 g/100 g) than other acidic or near neutral pH‐treated sample (30.06–32.30 g/100 g). The quality parameters such as biological value (67.62), and amino acid index (72.77) were higher for the SMPI treated at pH 10 as compared to the SMPI treated at other pH conditions. Hence, the pH‐treatment method can be utilized as an effective technique to improve the characteristics of SMPI, which will increases its applications in various food sectors.Practical ApplicationsThe current investigation demonstrated that pH‐shifting treatment had a substantial impact on the structural and nutritional quality of the soybean meal protein isolate extracted by ultrasonication. Improvements in soybean meal protein's surface hydrophobicity, free sulfhydryl groups, and secondary structural components will expand its uses in the dairy, bread, meat, and infant food development industries, among other food sectors as these structural changes improve the functionality of protein. Furthermore, the treatment of soybean meal protein isolate with pH shifting led to a considerable increase in nutritional quality, as measured by the essential amino acid composition, essential amino acid index, and protein efficiency ratio, which is expected to increase its utilization in novel food product development.

Conjugation of Soybean Proteins 7S/11S Isolate with Glucose/Fructose in Gels through Wet-Heating Maillard Reaction.

Conjugation with glucose (G) and fructose (F) via the Maillard reaction under the wet-heating condition is a natural and non-toxic method of improving the technological functions of 7S/11S proteins in different kinds of gels. It may be used as an affordable supply of emulsifiers and an excellent encapsulating matrix for gels. This study aimed to create a glucose/fructose-conjugated 7S/11S soy protein via the Maillard reaction. The conjugation was confirmed by determining the SDS-PAGE profile and circular dichroism spectra. In addition, these conjugates were comprehensively characterized in terms of grafting degree, browning degree, sulfhydryl content, surface hydrophobicity (H0), and differential scanning calorimetry (DSC) through various reaction times (0, 24, 48, and 72 h) to evaluate their ability to be used in food gels. The functional characteristics of the 7S/11S isolate-G/F conjugate formed at 70 °C, with a high degree of glycosylation and browning, were superior to those obtained at other reaction times. The SDS-PAGE profile indicated that the conjugation between the 7S and 11S proteins and carbohydrate sources of G and F through the Maillard reaction occurred. Secondary structural results revealed that covalent interactions with G and F affected the secondary structural components of 7S/11S proteins, leading to increased random coils. When exposed to moist heating conditions, G and F have significant potential for protein alteration through the Maillard reaction. The results of this study may provide new insights into protein modification and establish the theoretical basis for the therapeutic application of both G and F conjugation with soy proteins in different food matrixes and gels.

Rapid quantitative analysis of soybean protein isolates secondary structure by two-dimensional correlation infrared spectroscopy through pH perturbation

The infrared spectroscopy (IR) signal of protein is prone to being covered by impurity signals, and the accuracy of the secondary structure content calculated using spectral data is poor. To tackle this challenge, a rapid high-precision quantitative model for protein secondary structure was proposed. Firstly, a two-dimensional correlation calculation was performed based on 60 groups of soybean protein isolates (SPI) infrared spectroscopy data, resulting in a two-dimensional correlation infrared spectroscopy (2DCOS-IR). Subsequently, the optimal characteristic bands of the four secondary structures were extracted from the 2DCOS-IR. Ultimately, partial least squares (PLS), long short-term memory (LSTM), and bidirectional long short-term memory (BILSTM) algorithms were used to model the extracted characteristic bands and predict the content of SPI secondary structure. The findings suggested that BILSTM combined with 2DCOS-IR model (2DCOS-BILSTM) exhibited superior predictive performance. The prediction sets for α-helix, β-sheet, β-turn, and random coil were designated as 0.9257, 0.9077, 0.9476, and 0.8443, respectively, and their corresponding RMSEP values were 0.26, 0.48, 0.20, and 0.15. This strategy enhances the precision of IR and facilitates the rapid identification of secondary structure components within SPI, which is vital for the advancement of protein industrial production.

Investigation of the potential mechanisms of α-amylase and glucoamylase through ultrasound intensification

The aim of this study is to enhance the efficiency of enzymes, reduce operational costs, and increase production output. Experimental research shows that ultrasound positively impacted the activity of α-amylase and glucoamylase, with the peak α-amylase activity observed at 30 W for 5 min and the highest glucoamylase activity at 60 W for 3 min. Ultrasonication extended the optimal temperature of both enzymes, but had no effect on the optimal pH. According to the kinetic experiments, ultrasonic treatment could improve the catalytic efficiency of α-amylase and glucoamylase. Furthermore, the SDS-PAGE results revealed that ultrasound treatment did not alter the molecular weights of the enzymes and their primary structures; The circular dichroism and fluorescence spectroscopy analysis indicated the secondary structural components, especially the α-sheet and the tryptophan fluorescence intensity, were notably affected by ultrasound. The changes in the secondary and tertiary structure of α-amylase and glucoamylase suggest that ultrasonic treatment may enhance their activities. Our findings provide a theoretical basis for the efficient utilization of α-amylase and glucoamylase through understanding the enzyme structure changes after ultrasound.

Characterization, Anti-glycation, Anti-inflammation, and Lipase Inhibitory Properties of Rauvolfia vomitoriaLeaf Extract: In Vitro and In Silico Evaluations for Obesity Treatment.

Pancreatic lipase (PLP) is an enzyme responsible for the catalytic hydrolysis of fats and its inhibition is relevant for obesity management. Side effects linked with orthodox inhibitors have, however, paved the way for an increased search for safe natural sources. The present study investigated the anti-glycation, anti-inflammatory, and anti-lipase properties of Rauvolfia vomitoria aqueous (ARV), ethanolic (ERV), and methanolic (MRV) leaf extracts coupled with the molecular interactions of selected bioactive compounds with PLP using in vitro and in silico techniques. Phytochemical constituents were characterized using spectroscopic techniques. Drug-likeness and chemical reactivity profile of selected bioactive compounds were analyzed using SwissADME and quantum chemical calculations. FT-IR and GC-MS affirmed the presence of phenolic compounds including 3-phenyl-2-ethoxypropylphthalimide and 5-methyl-2-phenyl-1H-indole. All extracts showed moderate anti-glycation, anti-inflammatory, and lipase inhibitory capacities relative to standard controls. However, MRV exhibited the highest lipase inhibition (IC50, 0.17 ± 0.01mg/mL), using a mixed-inhibition pattern. MRV interaction with PLP resulted in decreased secondary structure components of PLP (α-sheet, β-turn). MRV compounds (MCP20, MCP28, etc.) exhibited low chemical hardness, EHOMO-ELUMO energy gap, and high chemical reactivity. Foremost MRV compounds obeyed Lipinski's rule of five for drug-likeness and interacted with PHE-78 amongst others at PLP catalytic domain with high binding affinity (≥ - 9.3kcal/mol). Pi-alkyl hydrophobic interaction and hydrogen bonding were predominantly involved. Our findings provide scientific insights into the ethnotherapeutic uses of R. vomitoria extracts for the management of obesity and related complications, plus useful information for optimizable drug-like candidates against obesity.

Unveiling the structure and interactions of SOG1, a NAC domain transcription factor: An in-silico perspective

SOG1 is a crucial plant-specific NAC domain family transcription factor and functions as the central regulator of DNA damage response, acting downstream of ATM and ATR kinases. In this study, various in-silico approaches have been employed for the characterization of SOG1 transcription factor in a comparative manner with its orthologues from various plant species. Amino acid sequences of more than a hundred SOG1 or SOG1-like proteins were retrieved and their relationship was determined through phylogenetic and motif analyses. Various physiochemical properties and secondary structural components of SOG1 orthologues were determined in selective plant species including Arabidopsis thaliana, Oryza sativa, Amborella trichopoda, and Physcomitrella patens. Furthermore, fold recognition or threading and homology-based three-dimensional models of SOG1 were constructed followed by subsequent evaluation of quality and accuracy of the generated protein models. Finally, extensive DNA-Protein and Protein-Protein interaction studies were performed using the HADDOCK server to give an insight into the mechanism of how SOG1 binds with the promoter region of its target genes or interacts with other proteins to regulate the DNA damage responses in plants. Our docking analysis data have shown the molecular mechanism of SOG1′s binding with 5′-CTT(N)7AAG-3′ and 5′-(N)4GTCAA(N)4-3′ consensus sequences present in the promoter region of its target genes. Moreover, SOG1 physically interacts and forms a thermodynamically stable complex with NAC103 and BRCA1 proteins, which possibly serve as coactivators or mediators in the transcription regulatory network of SOG1. Overall, our in-silico study will provide meaningful information regarding the structural and functional characterization of the SOG1 transcription factor.

Leveraging Indian pulse proteins for plant‐based mock meat III: physicochemical characterisation, FTIR spectra and texture profile analysis of meat analogues

SummaryThe current study was designed to supersede the meat protein with pulse‐based proteins and to determine the suitability of the processing method for commercialisation of plant protein meat analogues. The pulse protein concentrates (PPCs) were extracted from green gram, horse gram and cowpea using alkaline/isoelectric precipitation method. The PPCs were subjected for physicochemical, morphological, GC–MS and thermal analysis. The PPCs of green gram to horse gram to cowpea were used in the ratio of (20:20:20) T1, (30:15:15) T2 and (15:20:15) T3 to prepare deep‐fried meatballs. All the PPCs exhibited collapsed and wrinkled surface. The horse gram protein concentrates exhibited the highest denaturation temperature (Td °C) 89.50 ± 2.57 and enthalpy (ΔH (J g−1)) (287.73 ± 9.64) iterating better thermal stability compared to other samples. FTIR spectra indicated the presence of O–H stretching wide bands for mutton deep‐fried meatballs (3321.22 cm−1) and plant‐based deep‐fried meatballs (3288.28 cm−1), whereas PPCs in the region of (3275–3278 cm−1). Two C‐H bands and the main secondary structural components such as α‐helix, β‐sheet, β‐turn and random coil of PPCs were observed in the region of 1600–1700 cm−1. Amide N–H bending (1400–1500 cm−1) and the C–O stretching bands (1000–1300 cm−1) were observed for all the samples. The plant‐based deep‐fried meatball formulated at the ratio of 20:20:20 (T1) was closely related to the mutton deep‐fried meatballs in terms of organoleptic properties (colour, texture, juiciness and overall acceptability), colour properties (L* and b*) and textural properties such as hardness, adhesiveness and cohesiveness. These findings will open new research horizons in this area and pave the way for the commercialisation of meat substitutes, which will reduce the environmental impact and carbon footprint.

Adsorption behavior of serum proteins on anodized titanium is driven by surface nanomorphology.

Protein adsorption behavior can play a critical role in defining the outcome of a material by affecting the subsequent in vivo response to it. To date, the effect of surface properties on protein adsorption behavior has been mainly focused on surface chemistry, but research on the effect of nanoscale surface topography remains limited. In this study, the adsorption behavior of human serum albumin, immunoglobulin G, and fibrinogen in terms of the adsorbed amount and conformational changes were investigated on bare and anodized titanium (Ti) samples (40 and 60 V applied voltages). While the surface chemistry, RMS surface roughness, and arithmetic surface roughness of the anodized samples were similar, they had distinctly different nanomorphologies identified by atomic force microscopy and scanning electron microscopy, and the surface statistical parameters, surface skewness Ssk and kurtosis Sku. The Feret pore size distribution was more uniform on the 60 V sample, and surface nanostructures were more symmetrical with higher peaks and deeper pores. On the other hand, the 40 V sample surface presented a nonuniform pore size distribution and asymmetrical surface nanostructures with lower peaks and shallower pores. The amount of surface-adsorbed protein increased on the sample surfaces in the order of Ti < 40 V < 60 V with the predominant factor affecting the amount of surface-adsorbed protein being the increased surface area attained by pore formation. The secondary structure of all adsorbed proteins deviated from that of their native counterparts. While comparing the secondary structure components of proteins on anodized surfaces, it was observed that all three proteins retained more of their secondary structure composition on the surface with more uniform and symmetrical nanofeatures than the surface having asymmetrical nanostructures. Our results suggest that the nanomorphology of the peaks and outer walls of the nanotubes can significantly influence the conformation of adsorbed serum proteins, even for surfaces having similar roughness values.

Improvement of the quality of frozen dough for fried flour products by electrostatic field assisted freezing.

With the continuous development of the food industry, frozen dough technology has gradually become an indispensable part of dough processing, but its quality is often reduced due to freezing during the production process. Electrostatic field assisted freezing (EF) technology, as a key research project in recent years, reduces the physical damage of food materials by reducing or changing the size of ice crystals in frozen products. In this study, different intensities of electrostatic fields were used to assist in the repeated freezing and thawing process of dough. The effects of electrostatic fields on the freezing nucleation process were evaluated by measuring dough freezing curves, low field nuclear magnetic resonance, and melting enthalpy. Finally, it was found that the freezing time of frozen dough added with electrostatic field assisted freezing processing was shortened, the decrease rate of hardness, viscosity, and elasticity was reduced, and the indicators of water distribution and protein secondary structure components were closer to those of fresh dough. This experiment used electrostatic field assisted freezing to reduce the damage to the dough structure during the freezing process, improve the quality of frozen dough and fried products, and improve the freezing efficiency of frozen dough. It provides a new idea for the study of frozen dough. This article is protected by copyright. All rights reserved.

FTIR spectroscopic investigations of protein conformation provide clues of radioadaptation in the kidney of low-dose irradiated rats

Proteins comprise almost half of the weight of plasma membrane and are responsible for preforming various membrane functions. Functionality of the protein is sensitive to its structure. Therefore, modification of the protein conformation can abrogate its function. We demonstrate the induction of radioadaptation in the kidney of low-dose irradiated rats in the form of diminishing the alterations of the protein secondary structure. The FTIR amide I absorption band fitting using Lorentz function was used to identify the various components of the protein secondary structure. FTIR data show changes in amide I band position, amide I/amide II area ratio, FWHM of amide I band, the shifts in the β-structure bands at 1611, 1623, 1634 cm−1 and the decrease in the β/α ratio. 2Gy x-irradiation lead to an increase in the β-structure at the expense of the α-helix. The effect of 2Gy x-irradiation was diminished when preceded with 100 mGy x-rays 24 h earlier. The data provide clue of induction of radioadaptation in the kidneys of whole-body irradiated rats following receiving a low priming dose 24 h prior to a challenging dose.

Enhanced functionality of fermented whey protein using water kefir

ABSTRACT This research is part of an effort to enhance fermented whey proteins’ quality and nutritional value. In this research, we investigated the feasibility of using a natural fermentation approach on whey proteins. We determined the protein digestibility, non-nutritive compounds (including phenolic compounds and saponins), and microbiological quality of water kefir-fermented whey proteins. Due to the water kefir-induced fermentation of whey proteins, the protein digestibility improved from 88.48 to 94.33%. The protein quality of fermented whey proteins has been modified after the water kefir fermentation, as observed with the changes in the secondary protein structure components, especially α-helices (decreased from 10.58 to 8.52%) and random coil (increased from 12.25 to 17.33%). In addition, their water solubility, surface hydrophobicity, and surface charge changed significantly (P < .05) during the fermentation time; 88.44 to 94.11%, 387.23 to 272.7 a.u. and −30.06 to −34.93 mV, respectively. Furthermore, water kefir is an excellent source of fermenting microorganisms, including lactic and acetic acid bacteria and yeast. Thus, the water kefir fermentation approach could be an effective, practical, non-thermal approach for altering whey proteins.

Intrinsic disorder in the open reading frame 2 of hepatitis E virus: a protein with multiple functions beyond viral capsid

BackgroundHepatitis E virus (HEV) is the cause of a liver disease hepatitis E. The translation product of HEV ORF2 has recently been demonstrated as a protein involved in multiple functions besides performing its major role of a viral capsid. As intrinsically disordered regions (IDRs) are linked to various essential roles in the virus’s life cycle, we analyzed the disorder pattern distribution of the retrieved ORF2 protein sequences by employing different online predictors. Our findings might provide some clues on the disorder-based functions of ORF2 protein that possibly help us in understanding its behavior other than as a HEV capsid protein. ResultsThe modeled three dimensional (3D) structures of ORF2 showed the predominance of random coils or unstructured regions in addition to major secondary structure components (alpha helix and beta strand). After initial scrutinization, the predictors VLXT and VSL2 predicted ORF2 as a highly disordered protein while the predictors VL3 and DISOPRED3 predicted ORF2 as a moderately disordered protein, thus categorizing HEV-ORF2 into IDP (intrinsically disordered protein) or IDPR (intrinsically disordered protein region) respectively. Thus, our initial predicted disorderness in ORF2 protein 3D structures was in excellent agreement with their predicted disorder distribution patterns (evaluated through different predictors). The abundance of MoRFs (disorder-based protein binding sites) in ORF2 was observed that signified their interaction with binding partners which might further assist in viral infection. As IDPs/IDPRs are targets of regulation, we carried out the phosphorylation analysis to reveal the presence of post-translationally modified sites. Prevalence of several disordered-based phosphorylation sites further signified the involvement of ORF2 in diverse and significant biological processes. Furthermore, ORF2 structure-associated functions revealed its involvement in several crucial functions and biological processes like binding and catalytic activities. ConclusionsThe results predicted ORF2 as a protein with multiple functions besides its role as a capsid protein. Moreover, the occurrence of IDPR/IDP in ORF2 protein suggests that its disordered region might serve as novel drug targets via functioning as potential interacting domains. Our data collectively might provide significant implication in HEV vaccine search as disorderness in viral proteins is related to mechanisms involved in immune evasion.

Binding Investigation of Some Important Metal Ions Copper (I), Nickel (II), and Aluminium (III) with Bovine Serum Albumin Using Valid Spectroscopic Techniques

Studies based on the interaction of metals with proteins resulted in the development of promising metal-based compounds with encouraging medicinal potential. This study was aimed to utilize FT-IR and UV-Vis spectroscopic techniques to analyze the interactions of biologically significant metal ions, such as Al3+, Ni+2, and Cu+, with bovine serum albumin (BSA). Different concentrations of metal ions were interacted with BSA, and the complexes were analyzed using the two techniques. The change in the BSA secondary structure components such as β-sheet, β-antiparallel, α-helix, β-turn, and random coil were analyzed using second derivative resolution enhancement. The FT-IR spectroscopy suggested a marked decrease in the C=O stretching (corresponding to amide I) and C=N stretching (corresponding to amide II) intensities. Interestingly, upon complexation, a marked reduction (22.58–29.03%) in the α-helical component was observed with a considerable increase in the random coil component. The intensity of the absorption peak of BSA obtained using UV was observed to increase consecutively as the concentration of Cu+, Al3+, and Ni2+ ions increased. The binding constants for the BSA-Cu+, BSA-Ni+2, and BSA-Al+3 complexes were calculated to be 3.46 × 104 M−1, 1.28 × 104 M−1, and 2.08 × 104 M−1, respectively. It was concluded that the binding interaction decreased in the order Cu+ &gt; Al3+ &gt; Ni2+. These findings were similar to our previous findings using affinity capillary electrophoresis (ACE). Therefore, it can be inferred that the FT-IR and UV techniques might be utilised effectively to assess the metal-protein interaction and can have wide application in routine analysis. These techniques have several advantages in being simple, easy-to-perform, rapid, and affordable over other high-end techniques.

Bestsel: Updated webserver for secondary structure and fold prediction for protein CD spectroscopy.

Circular dichroism (CD) spectroscopy is widely used to characterize the secondary structure of proteins. Recently, we have developed the Beta Structure Selection (BeStSel) method to derive accurate and detailed structural information from the CD spectra which handles the spectral diversity of β-structured proteins. The BeStSel webserver provides a user-friendly and intelligent interface for the analysis of single or multiple CD spectra. Uniquely, BeStSel provides information on eight secondary structure components including parallel β-structure and antiparallel β-sheets with three different groups of twist. It overperforms any available methods in accuracy and information content, moreover, it is capable of predicting the protein fold down to the topology/homology level of the CATH classification. With the new versions of the DSSP and CATH databases, even more accurate estimates can be obtained using re-optimised basis spectra. A new module of the updated webserver helps to distinguish intrinsically disordered proteins by their CD spectrum. Users can also enter PDB IDs or upload structure files in PDB format as input to determine the corresponding secondary structure contents and fold classification, which help the experimental verification of protein MD and in silico modelling using CD spectroscopy. To aid correct concentration determination, extinction coefficients at 205 and 214 nm can be calculated from the primary sequence of the protein. The BeStSel server can be freely accessed at https://bestsel.elte.hu. This work was supported by National Research, Development and Innovation Fund of Hungary (K120391, KH125597, 2017-1.2.1-NKP-2017-00002, FIEK_16-1-2016-0005, TÉT_16-1-2016-0134, TÉT_16-1-2016-0197); SOLEIL Synchrotron, France (proposals 20171582, 20160916, 20151300, 20150515).

Conformational changes and physicochemical attributes of texturized pea protein isolate-konjac gum: With a new perspective of residence time during extrusion

The present study aimed to investigate the effects of different extrusion temperatures (110, 130 and 150 °C) and konjac gum addition (0.1 %, 0.2 %, and 0.3 %) on the flow behavior, physicochemical properties and microstructure of extruded pea protein isolate (PPI). The results showed that the textured protein could be improved by enhancing the extrusion temperature and adding konjac gum during extrusion. The water/oil holding capacity of PPI decreased and the SH content increased after extrusion. With temperature and konjac gum content increased, the β-sheet of extruded proteins transformed to other secondary structural components, and Trp residue transformed to a more polar environment, illustrating the changes in protein conformation. All extruded samples presented as yellow hue with little green and higher lightness, while excessive extrusion process reduced the brightness and promoted more formation of browning pigments. Extruded protein showed more associated layered with some air pores, and its hardness and chewiness increased with the increase of temperature and konjac gum concentration. Cluster analysis showed that the addition of konjac gum could effectively improve the quality characteristics of pea protein under low temperature extrusion, and the effect was similar to that of high temperature extrusion product. With the increase of konjac gum concentration, the flow pattern of protein extrusion gradually converted from plug flow to mixing flow, and the disorder degree of polysaccharide protein mixing system was enhanced. Moreover, Yeh-jaw model showed better fitting effect in F(θ) curves compared to Wolf-white.

In silico prediction, molecular modeling, and dynamics studies on the targeted next-generation sequencing identified genes underlying congenital heart disease in Down syndrome patients.

Individuals with Down syndrome (DS) have a 40%-60% chance of being born with congenital heart disease (CHD). This indicates that CHD in individuals with DS is not solely caused by trisomy 21, and there may be other genetic factors contributing to the development of CHD in these children. A study has identified variants in the specific genes that contribute to the pathogenesis of CHD in children with DS, isolated DS, and the CHD group. Computational studies on these identified variants, which, together with trisomy 21, determine the risk for CHD in DS cases, were limited. Here, we aimed to identify the impact of the identified variants that contribute to the pathogenesis of CHD in children with DS through in silico prediction, molecular modeling, and dynamics studies. The target single-nucleotide polymorphisms included in the study were examined for pathogenicity, residue conservation, and protein structural changes. The structural predictions were done using I-TASSER, Robetta, SWISS-MODEL, and Phyre2 tools. Further, the predicted models were validated through the PROCHECK server and molecular dynamics simulation using GROMACS software. The conservation analysis conducted on the identified variant highlights its significance in relation to the genetic disorders. Furthermore, a dynamics simulation study revealed the impact of the variant on protein structural stability (≤3 Å), providing valuable insights into its pathogenicity. We have also observed that the structure of the centrosomal protein of 290 kDa gene is relatively unstable, which may be attributed to its exclusive inclusion of helices within its secondary structural components. This computational study explores, for the first time, the association between genes and CHD-DS, evaluating the identified specific frameshift variants. The observed pathogenic mutations in CHD-DS patients require further experimental validation and may contribute to the development of prospective drug design research. The insights gained from the structural and functional implications of these variants could potentially serve as a cornerstone in the development of effective treatments for this debilitating condition.

Development of a reliability model for crack growth occurrence for a secondary hull component

Ship hull vibration is a major contributor to fatigue crack growth and main engine excitation is identified as an important vibration source. A general method to solve any vibration problem arising onboard a ship does not exist, which encourages the use of a reliability-based framework for assessing ship vibration and its consequences. A stochastic model of vibration response is developed for the probabilistic formulation of the failure probability of the occurrence of crack propagation of a secondary structural hull component. The secondary structural component considered is a pipe stack support. The pipe stack support connects a cargo pump pipe stack to the wall inside the cargo tank, and the support is welded directly onto this wall. First, a generic cargo hold model is analysed with engine speed and the relative distance between the engine and the structural component under consideration as stochastic variables. Then, submodels are used to investigate the local vibration of the support and the stress response is evaluated for a combination of different engine speeds and relative distances. A surface is fitted to the vibration response and used for probabilistic analysis by Monte Carlo (MC/DSPS) and FORM/SORM reliability methods. The limit state is formulated as the possibility of fatigue crack growth based on a threshold stress intensity factor. This threshold factor depends on the initial crack size and different initial sizes are investigated. The adequacy of the functional representation for the stochastic model, which is fitted to discrete data points, is also assessed. It is seen that a functional representation using a sum of sine terms give an adequate fit for describing the stress response induced by engine speed, while a polynomial representation was adequate for the relative distance variable. The failure probability estimated by Monte Carlo simulations and SORM indicates that the pipe stack support is not critical for the occurrence of fatigue crack growth. A main observation from the analysis is that the reliability-based design of secondary structural components, also looking at the interaction with the global structure, may help to improve the vibration-induced stresses in local hull details by application of proper design measures.

An investigation on the mechanical behaviour of sandwich composite structures with circular honeycomb bamboo core

Sandwich panels made with a bamboo core of different dimensions, packing geometries and facing materials are subjected to three-point bending tests and assessed through statistical and failure analysis. In addition to promoting a circular economy, this architecture holds great promise for replacing secondary structural components in sustainable construction and transportation facilities. The statistical analysis responses are associated with the equivalent density of the panels, flexural strength and modulus of the panels, skin stress and core shear strength and modulus. Individual bamboo rings are also characterised using physic mechanical and interfacial bonding tests. Treated aluminium face sheets provide the best mechanical performance compared to glass fibre-reinforced composite (GFRP) ones by increasing the overall properties of the sandwich panels. The specific face sheet material and void percentage affect the equivalent density, with lower values (~ 0.48 g/cm3) when using GFRP skins, larger bamboo rings and cubic packing. Sandwich panels with 30 mm bamboo rings and hexagonal packing provide higher flexural properties, i.e. ~ 43 MPa strength and ~ 7.6 GPa modulus, and skin stress (~ 288 MPa), while those with 20 mm bamboo rings have higher shear stiffness (~ 132 MPa) and resistance (~ 3.33 MPa). Sandwich panels made with aluminium skins show evident skin-polymer debonding, while those with GFRP have premature skin failure and lower structural performance. The proposed sandwich panels present remarkable and competitive mechanical performance concerning commercial analogous structures, generally used in the aeronautical and automotive industries.

The recovery effect of Vitamin C on structural alterations due to Streptozotocin-Induced diabetes in rat testicular tissues

Type I Diabetes is a multisystem disease that causes alterations in carbohydrate, protein, and fat metabolisms due to hyperglycemia. It has an extensive pathology, especially the mechanism involving oxidative stress is still complex. Type I diabetes is correlated with increased formation of free radicals and decreased levels of antioxidant potential. Vitamin C (Vit C) is a powerful antioxidant that participates in antioxidant defense, protecting lipid membranes and proteins from oxidative damage by donating electrons to free radicals.The effect of type I diabetes and the recovery role of Vit C on the structure and composition of the biomolecular content of testicular tissue is still unknown. Therefore, the current study aimed to investigate the alterations in the biomolecules of rat testes due to Streptozotocin (STZ)-induced type I diabetes using Attenuated Total Reflectance (ATR)-Fourier Transform Infrared (FTIR) spectroscopy and histological staining. The results revealed that the biomolecular structure and composition of testicular tissue are highly affected due to the development of diabetes. We obtained decreased saturation levels and increased unsaturation index in the lipids indicating the presence of lipid peroxidation in the diabetic state. The elevated lipid peroxidation levels have been implicated in the pathogenesis of naturally occurring and chemically induced diabetes. On the other hand, the protein content of diabetic rat testicular tissue was shown to decrease considerably, indicating an increase in proteolysis processes. Supporting the ratio of protein structural and conformational change, protein secondary structural components were also found to alter substantially in the diabetic state. Diabetes was also shown to lead to a decrease in the content of nucleic acids compared to proteins. These diabetes-induced alterations were found to be substantially recovered with the administration of Vit C. Although different doses and administration types of Vit C have been reported in the literature, there is no consensus yet. Therefore, we used three different doses of Vit C in our study as high (100 mg/kg/day), medium (50 mg/kg/day) and low (15 mg/kg/day) doses intraperitoneally in the present study, and the medium dose was found to be the most effective in the recovery from the diabetes-induced structural damages on rat testicular tissue. Vit C may have a therapeutic effect to be used as a complementary therapy in the treatment of diabetes.

CNT-Reinforced Self-Healable Epoxy Dynamic Networks Based on Disulfide Bond Exchange.

The design and utilization of polymers with healing capability have drawn increasing attention owing to their enhanced chain mobility and opportunity to heal minor cracks in composites. Rehealable thermoset polymers promise reduction in the maintenance cost and thus prolonged lifetime, reshaping, and recyclability. Introducing reversible covalent bonds is the mainstay strategy to achieve such plasticity in crosslinked polymers. Herein, we report a dynamic epoxy, which includes associative covalent adaptive networks (CANs) based on disulfide exchange bonds. Epoxy resin is chosen to study rehealing, as it is one of the most critical thermosetting polymers for various industries from aerospace to soft robotics. This study enlightens us about not only the consequences of CANs in the epoxy but also various factors such as soft segments and carbon nanotubes (CNTs). Epoxy dynamic networks are investigated in an attempt to explore the synergistic effect of the soft-segmented resins and CNTs on the healing and reshaping characteristics of epoxy networks along with varying stiffness. This research discusses epoxy dynamic networks in three main aspects: crosslink density, CAN density, and CNTs. Introducing soft segments into the epoxy network enhances the healing efficiency due to the increased chain mobility. A higher CAN density accelerates network rearrangement, improving the healing efficiency. It should also be noted that even with a low weight fraction of nanotubes, CNT-reinforced samples restored their initial strength more than neat samples after healing. The tensile strength of dynamic networks is at least 50 MPa, which is significant for their utility in primary or secondary structural components.