Concentrations Of Sodium Deoxycholate Research Articles

Insight into the Effect of Submicellar Concentrations of Sodium Deoxycholate on the Structure, Stability, and Activity of Bovine and Human Serum Albumin: An Interesting Comparison between Single and Double Tryptophan Proteins.

The progressive escalation in the applications of bile salts in diverse fields has triggered research on their interaction with various biological macromolecules, especially with proteins. A proper understanding of the interaction process of bile salts, particularly in the lower concentrations range, with the serum albumin seems important since the normal serum concentration of bile salts is approximately in the micromolar range. The current study deals with a comprehensive and comparative analysis of the interaction of submicellar concentrations of sodium deoxycholate (NaDC) with two homologous transport proteins: bovine serum albumin (BSA) and human serum albumin (HSA). HSA and BSA with one and two tryptophans, respectively, provide the opportunity for an interesting comparison of tryptophan fluorescence behavior on interaction with NaDC. The study suggests a sequential interaction of NaDC in three discrete stages with the two proteins. A detailed study using warfarin and ibuprofen as site markers provides information about the sites of interaction, which is further confirmed by inclusive molecular dynamics simulation analysis. Moreover, the comparison of the thermodynamics and stability of the NaDC-serum albumin complexes confirms the stronger interaction of NaDC with BSA as compared to that with HSA. The differential interaction between the bile salt and the two serum albumins is further established from the difference in the extent of decrease in the esterase-like activity assay of the proteins in the presence of NaDC. Therefore, the present study provides important insight into the effect of submicellar concentrations of NaDC on the structure, stability, and activity of the two homologous serum albumins and thus can contribute not only to the general understanding of the complex nature of serum albumin-bile salt interactions but also to the design of more effective pharmaceutical formulations in the field of drug delivery and biomedical research.

High-Yield Synthesis of Phosphatidylserine in a Well-Designed Mixed Micellar System.

A sustainable enzymatic system is essential for efficient phosphatidylserine (PS) synthesis in industrial production. Conventional biphasic systems face challenges such as excessive organic solvent usage, enzyme-intensive processes, and increased costs. This study introduces a novel approach using chitin nanofibrils (ChNFs) as an immobilization material for phospholipase D (PLD) in a mixed micellar system stabilized by the food-grade emulsifier sodium deoxycholate (SDC). The immobilized enzyme, ChNF-chiA1, was quickly prepared in a one-step process, eliminating the need for purification. By optimizing the reaction conditions, including l-Ser concentration (1.0 M), SDC concentration (10 mM), reaction time (8 h), and enzyme dosage (1.0 U), a remarkable PS yield of 96.74% was achieved in the solvent-free mixed micellar system. The catalytic efficiency of ChNF-chiA1 surpassed that of the free PLD-chiA1 biphasic system by 6.0-fold. This innovative and green biocatalytic technology offers a reusable solution for the high-value enzymatic synthesis of phospholipids, providing a promising avenue for industrial applications.

Brain targeting of zolmitriptan via transdermal terpesomes: statistical optimization and in vivo biodistribution study by 99mTc radiolabeling technique

Zolmitriptan (ZT) is a potent second generation triptan, commonly administered to alleviate migraine attacks. ZT suffers various limitations; massive hepatic first pass metabolism, P-gp efflux transporters susceptibility, and limited (≈40%) oral bioavailability. Transdermal route of administration could be explored to enhance its bioavailability. A 23.31 full factorial design was constructed to developed twenty-four ZT loaded terpesomes via thin film hydration technique. The influence of drug: phosphatidylcholine ratio, terpene type, terpene concentration and sodium deoxycholate concentration on the characterization of the developed ZT-loaded terpesomes was assessed. Particle size (PS), zeta potential (ZP), ZT entrapment efficiency (EE%), drug loading (DL%) and drug released percentages after 6 h (Q6h) were the selected dependent variables. Further morphological, crystallinity, and in-vivo histopathological studies were conducted for the optimum terpesomes (T6). 99mTc-ZT and 99mTc-ZT-T6 gel were radio-formulated for in-vivo biodistribution studies in mice following transdermal application of 99mTc-ZT-T6 gel, relative to 99mTc-ZT oral solution. T6 terpesomes [comprising ZT and phosphatidylcholine (1:15), cineole (1% w/v) and sodium deoxycholate (0.1% w/v)] were optimum with respect to spherical PS (290.2 nm), ZP (-48.9 mV), EE% (83%), DL% (3.9%) and Q6h (92.2%) with desirability value of 0.85. The safety of the developed T6 terpesomes was verified by the in-vivo histopathological studies. 99mTc-ZT-T6 gel showed maximum brain concentration (5 ± 0.1%ID/ g) with highest brain to blood ratio of 1.92 ± 0.1 at 4 h post transdermal application. Significant improvement of ZT brain relative bioavailability (529%) and high brain targeting efficiency (315%) were revealed with 99mTc-ZT-T6 gel, which confirmed successful ZT delivery to the brain. Terpesomes could be safe, successful systems capable of improving ZT bioavailability with high brain targeting efficiency.Graphical

Decoupling Individual Optical Nanosensor Responses Using a Spin-Coated Hydrogel Platform.

Significant advances have been made in fields such as nanotechnology and biomedicine using the unique properties of single-walled carbon nanotubes (SWCNTs). Specifically, SWCNTs are used as near-infrared fluorescence sensors in the solution phase to detect a wide array of biologically relevant analytes. However, solution-based sensing has several limitations, including limited sensitivity and poor spatial resolution. We have therefore devised a new spin-coated poly(ethylene glycol) diacrylate (PEG-DA) hydrogel platform to examine individual DNA-functionalized SWCNTs (DNA-SWCNTs) in their native aqueous state and have subsequently used this platform to investigate the temporal modulations of each SWCNT in response to a model analyte. A strong surfactant, sodium deoxycholate (SDC), was chosen as the model analyte as it rapidly exchanges with DNA oligonucleotides on the SWCNT surface, modulating several optical properties of the SWCNTs and demonstrating multiparameter analyte detection. Upon addition of SDC, we observed time-dependent spectral modulations in the emission center wavelengths and peak intensities of the individual SWCNTs, indicative of a DNA-to-surfactant exchange process. Interestingly, we found that the modulations in the peak intensities, as determined by kinetic data, were significantly delayed when compared to their center wavelength counterparts, suggesting a potential decoupling of the response of these two spectral features. We used a 1-D diffusion model to relate the local SDC concentration to the spectral response of each SWCNT and created dose-response curves. The peak intensity shifts at a higher SDC concentration than the center wavelength, indicating a potential change in the conformation of the surfactant molecules adsorbed to the SWCNT sidewall after the initial exchange process. This platform allows for a unique single-molecule analysis technique that is significantly more sensitive and modifiable than utilizing SWCNTs in the solution phase.

Aqueous two-phase extraction of single-walled carbon nanotubes using nonionic surfactant Tween 60

<p indent="0mm">Due to its excellent electronic and optical properties, single-walled carbon nanotubes (SWNTs) have attracted extensive attention. Since the property of SWNTs is determined by their structures, applications like high-performance devices require SWNTs with identical structures and uniform properties. Therefore, the sorting of SWNTs is of great significance. Aqueous two-phase (ATP) extraction is an emerging method that can be utilized to realize the structure sorting of SWNTs. ATP extraction is a repeatable and reliable technique that does not require state-of-the-art equipment. It is efficient and easy to scale up. In this article, by adjusting the concentration of sodium deoxycholate (DOC) and nonionic surfactant Tween 60, the diameter sorting of SWNTs and the separation of high purity (6,5) tubes were achieved. The sorting can be carried out at a higher DOC concentration, which could improve the competitive coating between DOC and Tween 60 on the surface of SWNTs, and further improve the sorting efficiency of the co-surfactant system. The comparison of the separation results between the Tween 60-DOC surfactant system and the SDS-DOC surfactant system shows that the introduction of nonionic surfactant Tween 60 is beneficial to the separation of higher purity (6,5) tubes.

Evidence for Involvement of the Salmonella enterica Z-Ring Assembly Factors ZapA and ZapB in Resistance to Bile.

Genes annotated as ygfE and yiiU in the genome of Salmonella enterica serovar Typhimurium encode proteins homologous to Escherichia coli cell division factors ZapA and ZapB, respectively. ZapA− and ZapB− mutants of S. enterica are bile-sensitive. The amount of zapB mRNA increases in the presence of a sublethal concentration of sodium deoxycholate (DOC) while zapA mRNA remains unaffected. Increased zapB mRNA level in the presence of DOC is not caused by upregulation of zapB transcription but by increased stability of zapB mRNA. This increase is suppressed by an hfq mutation, suggesting the involvement of a small regulatory RNA. We provide evidence that such sRNA is MicA. The ZapB protein is degraded in the presence of DOC, and degradation appears to involve the Lon protease. We propose that increased stability of zapB mRNA in the presence of DOC may counter degradation of bile-damaged ZapB, thereby providing sufficient level of functional ZapB protein to permit Z-ring assembly in the presence of bile.

Novel Sodium Deoxycholate-Based Chemical Decellularization Method for Peripheral Nerve.

Decellularized peripheral nerve has been proven to be an effective clinical intervention for peripheral nerve repair and a preclinical cell carrier after spinal cord injury. However, there are currently a lack of decellularization methods for peripheral nerve that remove cells and maintain matrix similar to the previously established, clinically translated technique (the Hudson method) that relies on the discontinued Triton X-200 detergent. Therefore, the aim of this study was to optimize a novel chemical decellularization method for peripheral nerves based on the currently available anionic detergent sodium deoxycholate. Sprague Dawley rat sciatic nerves were isolated, frozen in buffered solution, and then subject to sequential washes in water, salt buffer, zwitterionic detergents sulfobetaines -10 and -16, and varying concentrations of sodium deoxycholate (SDC). To optimize DNA removal after SDC decellularization, nerves were subjected to deoxyribonuclease (DNase) incubation and salt buffer washes. Immunohistochemical results demonstrated that utilization of 3% SDC in the decellularization process preserved extracellular matrix (ECM) components and structure while facilitating significantly better removal of Schwann cells, axons, and myelin compared with the Hudson method. The addition of a 3-h DNase incubation to the 3% SDC decellularization process significantly removed cellular debris compared with the Hudson method. Proteomic analysis demonstrated that our novel decellularization method based on 3% SDC +3-h DNase used in conjunction with zwitterionic detergents, and salt buffers (new decellularization method using 3% SDC + 3-h DNase, zwitterionic detergents, and salt buffers [SDD method]) produced a similar proteomic profile compared with the Hudson method and had significantly fewer counts of cellular proteins. Finally, cytotoxicity analysis demonstrated that the SDD decellularized scaffolds do not contain significant cytotoxic residuals as eluted media supported metabolically active Schwann cells in vitro. Overall, this study demonstrates that SDD decellularization represents a novel alternative utilizing currently commercially available chemical reagents. Impact Statement Decellularized nerves are clinically relevant materials that can be used for a variety of regenerative applications such as peripheral nerve and spinal cord injury repair. However, discontinuation of key detergents used in a proven chemical decellularization process necessitates the optimization of an equivalent or better method. This research presents the field with a novel chemical decellularization method to replace the previous validated standard. Scaffolds generated from this method provide an extracellular matrix-rich material that can be used in a variety of in vitro applications to understand cellular behavior and in vivo applications to facilitate regeneration after neural injury.

ENHANCEMENT OF SKIN PERMEABILITY OF ECONAZOLE NITRATE USING NOVEL FLEXISOMAL NANOCARRIERS BY IMPLEMENTING QUALITY BY DESIGN (QBD) APPROACH

Objective: The purpose of this study was an implementation of quality by design (QbD) for the formulation and characterization of econazole nitrate loaded flexisomal nanocarriers (EN-FS) to improve antifungal activity and to enhance skin permeability.&#x0D; Methods: Initially quality target product profile (QTTP) elements were identified and later critical quality attributes (CQA) elements were defined from QTPP elements. Particle size, entrapment efficiency and deformability index were defined as CQAs. Risk assessment was performed by using fishbone diagram and failure mode and effect analysis (FMEA). Design space was created by using fractional factorial design 25-2 as screening design and 32 full factorial design as optimization design to optimize two variables soya phosphatidylcholine concentration(X1) and sodium deoxycholate concentration (X2).&#x0D; Results: Optimized batch of EN-FS was 249.5±3.48 nm, with entrapment efficiency of 88.6±0.89 % and deformability index of 31.75±0.98. Zeta potential analysis showed value of-22.5 mV. Morphological analysis by TEM showed spherical shaped flexisomes, which confirmed the vesicular characteristics. The optimized batch of EN-FS was further made into hydrogels by using sepineo P600 as gelling agent. The % drug diffusion of EN-FS hydrogels had shown 24.68%. With higher skin deposition and higher value of zone of inhibition in antifungal study as compared to plain EN hydrogel. CLSM studies indicated deep penetration of EN-FS in skin layers. Lastly control strategy for EN-FS were developed.&#x0D; Conclusion: It was concluded that EN-FS showed high flexibility and enhanced antifungal activity therefore found to be a potential nanocarriers for drug deposition in skin layers without disturbing skin integrity.

GYY4137 Attenuates Sodium Deoxycholate-Induced Intestinal Barrier Injury Both In Vitro and In Vivo.

Objectives Substantial studies have demonstrated that an elevated concentration of deoxycholic acid (DCA) in the colonic lumen may play a critical role in the pathogenesis of intestinal barrier dysfunction and inflammatory bowel disease (IBD). The purpose of this study was to investigate the protective effects of GYY4137, as a novel and synthetic H2S donor, on the injury of intestinal barrier induced by sodium deoxycholate (SDC) both in vivo and in vitro. Methods In this study, Caco-2 monolayers and mouse models with high SDC concentration in the lumen were used to study the effect of GYY4137 on intestinal barrier dysfunction induced by SDC and its underlying mechanisms. Results In Caco-2 monolayers, a short period of addition of SDC increased the permeability of monolayers obviously, changed distribution of tight junctions (TJs), and improved the phosphorylation level of myosin light chain kinase (MLCK) and myosin light chain (MLC). However, pretreatment with GYY4137 markedly ameliorated the SDC-induced barrier dysfunction. Being injected with GYY4137 could enable mice to resist the SDC-induced injury of the intestinal barrier. Besides, GYY4137 promoted the recovery of the body weight and intestinal barrier histological score of mice with the gavage of SDC. GYY4137 also attenuated the decreased expression level of TJs in mice treated with SDC. Conclusion Taken together, this research suggests that GYY4137 preserves the intestinal barrier from SDC-induced injury via suppressing the activation of P-MLCK-P-MLC2 signaling pathway and increasing the expression level of tight junctions.

Probiotic Potential Test for Lactic Acid Bacterial Isolate from Labi Cattle Gastric Again Low Acidity and Sodium Deoxycholate

Lactic acid bacteria (LAB) are one of group probiotic bacteria, which have a positive impact on human and animal health. The aim of this research was to determine the potency lactic acid bacterial isolate from LABi cattle gastric as a probiotic that have resistance to low pH and sodium deoxycholate. The study was started with the cultivation test that aims to made sure uncontaminated isolates of microorganisms, including test for growth response in MRS broth medium, test on catalase production, and Gram stain. Its potency for probiotic development was tested by growing of isolate in MRS broth medium with low pH conditions (pH 2, 3, 4) and in MRS medium supplemented with various concentration of sodium deoxycholate (0,2 mM, 0,4 mM, 0,6 mM). The result showed that isolate from LABi cattle gastric was able to grow well in MRS broth medium under anaerobic condition. In addition, it also showed catalase negative and Gram-positive bacteria. In the main experiment, this isolate was found to be resistant to low pH conditions (up to pH 2) and high concentration of sodium deoxycholate (up to 0,6 mM). These results indicate that the isolate the lactic acid bacteria have resistance to low pH and the sodium deoxycholate, which is the main requirement of the probiotic bacteria

Viability RT-qPCR Combined with Sodium Deoxycholate Pre-treatment for Selective Quantification of Infectious Viruses in Drinking Water Samples.

The presence of pathogenic viruses in drinking water is a major public health concern. Although viability RT-qPCR methods were developed to quantify infectious viruses, they may not always reflect viral infectivity, therefore leading to false-positive results. In this study, sodium deoxycholate (SD) pre-treatment was used to improve the efficiency of viability RT-qPCR methods with respect to exclusive quantification of infectious viruses. The ability of SD pre-treatment to enhance the penetration of three viability markers, namely, ethidium monoazide (EMA, 100µM), propidium monoazide (PMA, 100µM), and cis-dichlorodiammineplatinum (CDDP, 1000µM), into heat-treated (90°C for 1min) Aichi virus at various concentrations (0.01-0.5%) was evaluated. The optimal SD concentration was found to be 0.1% for all markers. EMA/PMA/CDDP-RT-qPCR with 0.1% SD pre-treatment was significantly more effective than without SD pre-treatment in determining AiV inactivation after heat (50, 60, 70, 80, or 90°C for 1min) or chlorine treatment (1 mgCl2/L for 1, 2, 5, or 10min). Among the viability RT-qPCR methods tested, CDDP-RT-qPCR with SD pre-treatment (SD-CDDP-RT-qPCR) was the most effective in reflecting viral infectivity. Performance testing of SD-CDDP-RT-qPCR in concentrated drinking water samples did not reveal any significant effects of SD-CDDP treatment. Thus, SD-CDDP-RT-qPCR could be a useful tool for monitoring infectious virus presence in drinking water.

Purification of β‐carotene 15,15′‐monooxygenase from pig intestine and its enzymatic hydrolysis of pigment in soybean oil

Summaryβ‐Carotene 15,15′‐monooxygenase was isolated and purified from the intestinal mucosa of pigs, and then, it was applied to hydrolyse the pigment in soybean oil, and thus, vitamin A fortified soybean oil was obtained. The pig intestinal mucosal protein solution was purified to a specific activity of 2.487 × 10−4 U mg−1, maximum reaction velocity (Vmax) of 8.42 × 10−9 mol/h and Michaelis constant (Km) of 2.03 × 10−5 m. The protein solution had a molecular mass of 156 kDa by gel filtration. The sodium deoxycholate concentrations, optimum pH, Tween 40 amount and enzyme amount for vitamin A production in soybean oil were determined to be 6.0 mm, 8.0, 3.0% (w/v) and 0.2 U/mL enzyme, respectively. Under these conditions, β‐carotene 15,15′‐monooxygenase produced 14.65 mg/L vitamin A after 20 h, with a conversion yield of β‐carotene of 33.29% (w/w). Therefore, the nutrients in soybean oil were improved.

Peptide-based hydrogels with tunable nanostructures for the controlled release of dyes

Hydrogels with different microstructures including nanoribbons, stiff nanofibers, helical ribbons and nanotubes were observed by varying the concentration of oxidized glutathione (OGH) with a fixed concentration of sodium deoxycholate (SD). The self-assembled nanostructures were characterized in detail by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Random coil structures and β-sheets play important roles in the constructed nanostructures, which were verified by Fourier-transform infrared (FT-IR) spectroscopy and circular dichroism (CD), as well as small angle X-ray diffraction (SXRD) measurements. We proposed a mechanism for these nanostructural transformations. The "weak hydrogels" exhibited irreversible responses to heating and shaking and a reversible response to pH. Furthermore, the hydrogel could be used for the controlled release of dyes. Due to the strong electrostatic attraction between the positively charged dye methylene violet (MV) and the negatively charged nanofibers, methylene violet is released more slowly than the negatively charged dye, methyl orange (MO).

Transdermal Delivery of Ondansetron Hydrochloride via Bilosomal Systems: In Vitro, Ex Vivo, and In Vivo Characterization Studies.

Ondansetron hydrochloride (OND) is commonly used for management of postoperative and chemotherapeutic-induced nausea and vomiting. It suffers from low bioavailability (60%) and rapid elimination (t1/2; 3-4h). The current work aimed to develop OND-loaded bilosomes as a promising transdermal delivery system capable of surmount drug limitations. The variables influencing the development of OND-loaded bilosomes and niosomes (18 systems) via the thin film hydration technique were investigated, including surfactant type (Span®60 or Span®80), surfactant/cholesterol molar ratio (7:0, 7:1, or 7:3), and sodium deoxycholate (SDC) concentration (0, 2.5, or 5%, w/v). The systems were characterized for particle size, polydispersity index, zeta potential, drug entrapment efficiency (EE%), and in vitro permeation. Based on factorial analysis (32·21) and calculations of desirability values, six systems were further subjected to ex vivo permeation through excised rat skin, differential scanning calorimetry (DSC), powder x-ray diffraction (PXRD), and transmission electron microscopy. Histopathological and in vivo permeation studies in rats were conducted on the best achieved system (B6) in comparison to drug solution. Higher desirability values were achieved with Span® 60-based bilosomes, surfactant/cholesterol molar ratio of 7:1, and SDC concentration of 2.5% w/v with respect to small vesicle size, polydispersity index and high zeta potential, EE%, and cumulative drug permeation. OND was dispersed in amorphous state as revealed from DSC and PXRD studies. No marked effect was observed in rat skin following application of B6 system while higher ex vivo and in vivo cumulative permeation profiles were revealed. Bilosomal systems were considered as safe and efficient carriers for the transdermal delivery for OND.

Adaptation of Salmonella enterica to bile: essential role of AcrAB-mediated efflux.

Adaptation to bile is the ability to endure the lethal effects of bile salts after growth on sublethal concentrations. Surveys of adaptation to bile in Salmonella enterica ser. Tyhimurium reveal that active efflux is essential for adaptation while other bacterial functions involved in bile resistance are not. Among S. enterica mutants lacking one or more efflux systems, only strains lacking AcrAB are unable to adapt, thus revealing an essential role for AcrAB. Transcription of the acrAB operon is upregulated in the presence of a sublethal concentration of sodium deoxycholate (DOC) while other efflux loci are either weakly upregulated or irresponsive. Upregulation of acrAB transcription is strong during exponential growth, and weak in stationary cultures. Single cell analysis of ethidium bromide accumulation indicates that DOC-induced AcrAB-mediated efflux occurs in both exponential and stationary cultures. Upregulation of acrAB expression may thus be crucial at early stages of adaptation, while sustained AcrAB activity may be sufficient to confer bile resistance in nondividing cells.

Nanosized Liposomes Containing Bile Salt: A Vesicular Nanocarrier for Enhancing Oral Bioavailability of BCS Class III Drug.

Liposomes have been studied as a colloidal carrier in drug delivery systems, especially for oral administration. However, their low structural integrity in the gut is still a major shortcoming. Membrane disruptive effects of physiological bile salts in the small intestine result in premature drug release prior to intestinal absorption. Thus, we analyzed the stabilizing effect of sodium deoxycholate when incorporated into nano-sized liposomes. Cefotaxime-loaded liposomes were prepared with different sodium deoxycholate concentrations (3.75- 30 mM) by rotary film evaporation followed by nano-size reduction. The physical integrity of liposomes was evaluated by monitoring cefotaxime leakage, particle sizes in different simulated physiological media. The oral bioavailability and pharmacokinetics of cefotaxime was assessed in rats (n = 6 per group) after single dose of drug-encapsulated in liposomes containing bile salt, drug in conventional liposomes, and cefotaxime solution (oral and intravenous). Simulated gastric fluid with low pH showed less effect on the stability of liposomes in comparison to media containing physiological bile salts. Liposomes containing 15 mM sodium deoxycholate were most stable in size and retained the majority of encapsulated cefotaxime even in fed state of simulated intestinal fluid being the most destructive media. Pharmacokinetics data showed an increase in Cmax and AUC0-inf in the following order: cefotaxime solution < conventional liposomes < liposomes made with bile salts. The total oral bioavailability of cefotaxime in liposomes containing bile salt was found to be 5-times higher compared to cefotaxime solution and twice as much as in conventional liposomes. Incorporation of bile salts, initially used as membrane permeation enhancer, also acted as a stabilizer against physiological bile salts. The nano-sized liposomes containing sodium deoxycholate were able to reduce the leakage of encapsulated cefotaxime in the gut due to the improved vesicle stability and to enhance the oral bioavailability of acid-labile drugs up to 5-fold.This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Displacement Kinetics of Single-Stranded DNA Wrapped Around Carbon Nanotubes

Surface coatings on single-walled carbon nanotubes (SWCNTs) play key roles in their properties and applications. One of the most intriguing coatings is single-stranded DNA, which is known to helically wrap individual nanotubes with affinities that depend on oligonucleotide sequence and SWCNT structure. To better understand such selective interactions, we use fluorescence spectroscopy to monitor the kinetics of ssDNA displacement by sodium deoxycholate (SDC), a common surfactant. This displacement causes distinct changes in the wavelength and intensity of structure-specific SWCNT near-IR emission peaks. By quantifying the kinetics of these changes as a function of oligonucleotide sequence, oligonucleotide length, SWCNT structure, sample temperature, and SDC concentration, we have extracted sets of values for the activation enthalpy ∆H≠, activation entropy ∆S≠, and activation Gibbs free energy ∆G≠ for displacement of d(GT) n , with n ranging from 15 to 30. We find that rates of displacement decrease for longer oligonucleotides and drop sharply as nanotube diameter increases from 0.75 to 0.97 nm. These increases in ∆G≠ are attributed to increases in -T∆S≠ that exceed the decreases in ∆H≠ over this range. Remarkably, the kinetics also reveal a strong power-law dependence (up to 6th order) in SDC concentration, indicating a highly cooperative process for ssDNA displacement. We will present experimental results and a proposed mechanistic interpretation.

Environmental stimuli induced phase transition in the aqueous mixture solution of Gemini surfactants and sodium deoxycholate

The phase behavior in a mixture of a cationic Gemini surfactant (12-2-12) and an anionic sodium deoxycholate (SDC) in the aqueous solution was reported here. The microstructures of formed aggregates have been investigated by rheology, small angle X-ray scattering and transmission electron microscopy. Mediated by the hydrophobic and electrostatic interactions of 12-2-12 and SDC, the wormlike micelles and lamellar aggregates were formed successively with increasing the SDC concentration. Due to the presence of hydroxyl and carboxylate groups on SDC, these aggregates were temperature and pH responsive. At low SDC concentrations, the wormlike micelles could be transformed into lamellar aggregates at lower pH. While at high SDC concentrations, the lamellar aggregates would be transformed into wormlike micelles at elevated temperatures. The Gemini surfactant structure also played an important role here on such environment-responsive phase transitions. The obtained results suggest the possibility to form smart aggregates by utilizing simple molecules with certain functional groups.

Improvement of a sample preparation method assisted by sodium deoxycholate for mass-spectrometry-based shotgun membrane proteomics†

In current shotgun-proteomics-based biological discovery, the identification of membrane proteins is a challenge. This is especially true for integral membrane proteins due to their highly hydrophobic nature and low abundance. Thus, much effort has been directed at sample preparation strategies such as use of detergents, chaotropes, and organic solvents. We previously described a sample preparation method for shotgun membrane proteomics, the sodium deoxycholate assisted method, which cleverly circumvents many of the challenges associated with traditional sample preparation methods. However, the method is associated with significant sample loss due to the slightly weaker extraction/solubilization ability of sodium deoxycholate when it is used at relatively low concentrations such as 1%. Hence, we present an enhanced sodium deoxycholate sample preparation strategy that first uses a high concentration of sodium deoxycholate (5%) to lyse membranes and extract/solubilize hydrophobic membrane proteins, and then dilutes the detergent to 1% for a more efficient digestion. We then applied the improved method to shotgun analysis of proteins from rat liver membrane enriched fraction. Compared with other representative sample preparation strategies including our previous sodium deoxycholate assisted method, the enhanced sodium deoxycholate method exhibited superior sensitivity, coverage, and reliability for the identification of membrane proteins particularly those with high hydrophobicity and/or multiple transmembrane domains.

Bile-induced peptidoglycan remodelling in Salmonella enterica.

Changes in the peptidoglycan (PG) structure of Salmonella enterica are detected in the presence of a sublethal concentration of sodium deoxycholate (DOC): (i) lower proportions of Braun lipoprotein (Lpp)-bound muropeptides; (ii) reduced levels of muropeptides cross-linked by L(meso)-diaminopimelyl-D(meso)-diaminopimelic acid (L-D) peptide bridges (3-3 cross-links). Similar structural changes are found in S. enterica cultures adapted to grow in the presence of a lethal concentration of DOC, suggesting that reduced anchoring of Braun protein to PG and low occurrence of 3-3 cross-links may increase S. enterica resistance to bile. This view is further supported by additional observations: (i) A triple mutant lacking L,D-transpeptidases YbiS, ErfK, and YcfS, which does not contain Lpp anchored to PG, is hyper-resistant to bile; (ii) enhanced 3-3 cross-linking upon overexpression of YnhG transpeptidase causes a decrease in bile resistance. These observations suggest that remodelling of the cell wall may be added to the list of adaptive responses that permit survival of S. enterica in the presence of bile.