Polar Amino Acids Research Articles

Influence of polar amino acids on the carbonation of lime mortars

The addition of protein-based additives (e.g. milk, egg white, animal blood) into lime mortars can improve mortar properties such as workability, strengths and durability. With the intent to understand how and why proteinaceous additives improve lime mortar properties, it could be useful to start from the basic building blocks of proteins amino acids. Consequently, the present study focuses on the influence of polar amino acids on the carbonation of lime mortars, and the results demonstrated that addition of amino acids into mortars could slow down mortar drying, increase surface hardness, slow down carbonation, promote amorphous calcium carbonate stabilization and inhibit calcite formation; moreover, these effects seemed to become more evident with the increase of amino acid concentration. It was speculated that in highly alkaline lime mortars, polar amino acids could lime carbonation by interacting with calcium carbonate via H-bonds and additional Ca2+ mediated adsorption.

Effect of Secondary Structures on the Adsorption of Peptides onto Hydrophobic Solid Surfaces Revealed by SALDI-TOF and MD Simulations.

The adsorption of peptides and proteins on hydrophobic solid surfaces has received considerable research attention owing to their wide applications to biocompatible nanomaterials and nanodevices, such as biosensors and cell adhesion materials with reduced nanomaterial toxicity. However, fundamental understandings about physicochemical hydrophobic interactions between peptides and hydrophobic solid surfaces are still unknown. In this study, we investigate the effect of secondary structures on adsorption energies between peptides and hydrophobic solid surfaces via experimental and theoretical analyses using surface-assisted laser desorption/ionization-time-of-flight (SALDI-TOF) and molecular dynamics (MD) simulations. The hydrophobic interactions between peptides and hydrophobic solid surfaces measured via SALDI-TOF and MD simulations indicate that the hydrophobic interaction of peptides with random coil structures increased more than that of peptides with an α-helix structure when polar amino acids are replaced with hydrophobic amino acids. Additionally, our study sheds new light on the fundamental understanding of the hydrophobic interaction between hydrophobic solid surfaces and peptides that have diverse secondary structures.

Photobiocatalytic Cascades for Acylating N‐Heterocycles with Natural Amino Acids via the 2‐Keto Acids

AbstractPhotobiocatalysis fully utilizing the unique reactivity of photocatalysis and efficient transforming biobased feedstocks of biocatalysis represents a promising approach for future green synthesis. However, photobiocatalytic cascade with biobased starting substrates has been rarely reported. Here, we present photobiocatalytic cascades that modify the N‐heterocycle with keto acids biocatalytically synthesized from natural amino acids. The types of aliphatic, aromatic, and polar natural amino acids are compatible with the photobiocatalytic cascades system. In addition, the cascade is compatible with a range of N‐heterocycles with moderate to good yield (up to 82%). Furthermore, the cascade system can reach gram scale (0.91 g) with a good separation yield, demonstrating the potential for scaling up production to practical application. This photobiocatalytic cascade can synthesize a range of important N‐heterocyclic derivatives from natural amino acids in a green fashion and paves the way for greener synthesis by combining biocatalysis and photocatalysis.magnified image

Rice Bran and Its Potential To Complement the Nutritional Needs of Children and Elderly.

Rice bran is an agro-industrial by-product of low added value that can be used to complement human nutritional needs. In this work, the profile of minerals, fatty acids and amino acids in brown rice bran was determined, aiming to evaluate its potential to complement the nutritional needs of different age groups, according to recommendations of regulatory agencies. The brown rice bran was supplied by a rice processing industry located in the south of the state of Rio Grande do Sul. Minerals were quantified using an emission spectrometer; the fatty acid profile was determined by gas chromatography and the amino acids were quantified by high-performance liquid chromatography with fluorescence (HPLC-FL). The main minerals were phosphorus (P), magnesium (Mg), potassium (K) and calcium (Ca) (2,933, 1,029, 211 and 56mg / 100g of rice bran). Saturated, monounsaturated and polyunsaturated fatty acids in rice bran were 22.4, 36.2 and 34.5% of lipid content, respectively. The polar, neutral and charged amino acids represented 8.8, 9.3 and 12.8% of the protein content, respectively. The composition of this co-product of rice supply chain is a good alternative to the new demand on plant-based food supplying the recommended daily intake (RDI) of national and international food polices.

Deciphering the Alphabet of Disorder-Glu and Asp Act Differently on Local but Not Global Properties.

Compared to folded proteins, the sequences of intrinsically disordered proteins (IDPs) are enriched in polar and charged amino acids. Glutamate is one of the most enriched amino acids in IDPs, while the chemically similar amino acid aspartate is less enriched. So far, the underlying functional differences between glutamates and aspartates in IDPs remain poorly understood. In this study, we examine the differential effects of aspartate and glutamates in IDPs by comparing the function and conformational ensemble of glutamate and aspartate variants of the disordered protein Dss1, using a range of assays, including interaction studies, nuclear magnetic resonance spectroscopy, small-angle X-ray scattering and molecular dynamics simulation. First, we analyze the sequences of the rapidly growing database of experimentally verified IDPs (DisProt) and show that glutamate enrichment is not caused by a taxonomy bias in IDPs. From analyses of local and global structural properties as well as cell growth and protein-protein interactions using a model acidic IDP from yeast and three Glu/Asp variants, we find that while the Glu/Asp variants support similar function and global dimensions, the variants differ in their binding affinities and population of local transient structural elements. We speculate that these local structural differences may play roles in functional diversity, where glutamates can support increased helicity, important for folding and binding, while aspartates support extended structures and form helical caps, as well as playing more relevant roles in, e.g., transactivation domains and ion-binding.

Development of a Hybrid Biomimetic Enamel-Biocomposite Interface and a Study of Its Molecular Features Using Synchrotron Submicron ATR-FTIR Microspectroscopy and Multivariate Analysis Techniques.

Using a biomimetic strategy and bioinspired materials, our work proposed a new technological approach to create a hybrid transitional layer between enamel and dental biocomposite. For this purpose, an amino acid booster conditioner based on a set of polar amino acids (lysine, arginine, hyaluronic acid), calcium alkali, and a modified adhesive based on BisGMA and nanocrystalline carbonate-substituted hydroxyapatite are used during dental enamel restoration. The molecular properties of the hybrid interface formed using the proposed strategy were understood using methods of multivariate statistical analysis of spectral information collected using the technique of synchrotron infrared microspectroscopy. The results obtained indicate the possibility of forming a bonding that mimics the properties of natural tissue with controlled molecular properties in the hybrid layer. The diffusion of the amino acid booster conditioner component, the calcium alkali, and the modified adhesive with nanocrystalline carbonate-substituted hydroxyapatite in the hybrid interface region creates a structure that should stabilize the reconstituted crystalline enamel layer. The developed technology can form the basis for an individualized, personalized approach to dental enamel restorations.

Study on zinc ions binding to the individual casein fractions: αS1-, β- and κ-casein

The presented work is focused on the isotherm study on the Zn2+ ions binding to the individual casein fractions: αS1-, β- and κ-casein (αS1CN, βCN and κCN). The experimental isotherms were evaluated using Freundlich and Langmuir models. Subsequently, the stability of the obtained complexes in the respective Zn2+ ion concentrations (120, 350, 600 mg/L) was determined by carrying out zeta potential measurements. Capillary electrophoresis combined with inductively coupled plasma mass spectrometry (CE-ICP-MS) confirmed the occurring binding process. Additionally, physicochemical characteristics of the obtained metal-protein complexes was performed including scanning electron microscopy (SEM) in two modes (SE and Z-contrast) and the binding sites of caseins to Zn2+ ions were indicated using attenuated total reflectance infrared spectroscopy (FTIR-ATR) and Raman analysis as well as mass spectrometry technique (MALDI-TOF MS). Isothermal studies indicated a heterogeneously complex zinc ion adsorption process, and a stability study showed that the zeta potential is strongly related to the hydrophobicity, size and structure of the casein isoforms studied. Electron microscopy confirmed the modification of casein surfaces due to the addition of Zn2+ ions. Spectroscopic techniques indicated the interaction of zinc ions with polar amino acids of casein, such as glutamic acid (Glu) and aspartic acid (Asp), but also His, Cys. The influence of phosphate groups was also observed. Finally, the study culminated in a molecular docking study of the Zn2+ ion binding process, which confirmed the presence of the listed amino acids responsible for the binding process.

Responses of infective juveniles of the soybean cyst nematode (Heterodera glycines) and the root-knot nematodes (Meloidogyne hapla, M. incognita) to amino acids

Summary Plant-parasitic nematode infective juveniles (J2) use phytochemical signals released into the rhizosphere to locate host roots. Amino acids are the second most abundant metabolites of root exudates, but it is unknown if they are associated with J2 chemotaxis. In this study, J2 chemotaxis and mortality of the soybean cyst nematode (Heterodera glycines) and root-knot nematodes (Meloidogyne incognita and M. hapla) were examined in response to 15 amino acids and the corresponding pH values for tested amino acid solutions were measured. Responses varied by amino acid and among the species. Significant attraction, determined by J2 count within amino acid solution dispensers after 24 h exposure, occurred with 19 out of 45 J2-amino acid combinations. Heterodera glycines, M. hapla and M. incognita were attracted to nine, three and seven amino acids, respectively. Strongest attractions were to acidic polar amino acids aspartate and glutamate (H. glycines, M. hapla) and basic polar arginine (M. hapla), as previously reported, acid and basic pH attracting nematodes, thereby indicating that pH might be one of the attraction factors for these amino acids. All three nematodes exhibited clustering behaviours, such as halo or balling formations, just outside amino acid solution dispensers, with H. glycines, M. hapla and M. incognita responding to four, 12 and two amino acids, respectively. Six of 15 amino acid solutions, representing a range of pH values, caused increased mortality. Certain aspartate and glutamate affected both H. glycines and M. hapla; arginine, aspartate, cysteine, lysine, methionine affected M. incognita; and cysteine caused complete mortality in M. hapla. All the results suggest that amino acids affect nematode attraction and mortality.

Regulation of the Inevitable Water-Responsivity of Silk Fibroin Biopolymer by Polar Amino Acid Activation.

In nature, water is vital for maintaining homeostasis. Particularly, organisms (e.g., plant leaf, bird feather) exploit water fluidics for motions. Hydration-adaptive crystallization is the representative water-responsive actuation of biopolymers. This crystallization has inspired the development of intelligent human-robot interfaces. At the same time, it hinders the consistent adhesion of tissue adhesive. As hydration-adaptive crystallization is inevitable, the on-demand control of crystallization is desirable in the innovative biopolymeric biomedical systems. To this end, this study developed an amino acid-based technology to artificially up- or down-regulate the inevitable crystallization of silk fibroin. A case II diffusion model was constructed, and it revealed that the activity of polar amino acid is related to crystallization kinetics. Furthermore, the water dynamics study suggested that active amino acid stabilizes crystallization-triggering water molecules. As a proof-of-concept, we verified that a 30% increase in the activity of serine resulted in a 50% decrease in the crystallization rate. Furthermore, the active amino acid-based suppression of hydration-adaptive crystallization enabled the silk fibroin to keep its robust adhesion (approximately 160 kJ m-3) by reducing the water-induced loss of adhesive force. The proposed silk fibroin was demonstrated as a stable tissue adhesive applied on ex vivo porcine mandible tissue. This amino acid-based regulation of hydration-adaptive crystallization will pioneer next-generation biopolymer-based healthcare.

A Statistical Analysis of the Sequence and Structure of Thermophilic and Non-Thermophilic Proteins.

Thermophilic proteins have various practical applications in theoretical research and in industry. In recent years, the demand for thermophilic proteins on an industrial scale has been increasing; therefore, the engineering of thermophilic proteins has become a hot direction in the field of protein engineering. However, the exact mechanism of thermostability of proteins is not yet known, for engineering thermophilic proteins knowing the basis of thermostability is necessary. In order to understand the basis of the thermostability in proteins, we have made a statistical analysis of the sequences, secondary structures, hydrogen bonds, salt bridges, DHA (Donor–Hydrogen–Accepter) angles, and bond lengths of ten pairs of thermophilic proteins and their non-thermophilic orthologous. Our findings suggest that polar amino acids contribute to thermostability in proteins by forming hydrogen bonds and salt bridges which provide resistance against protein denaturation. Short bond length and a wider DHA angle provide greater bond stability in thermophilic proteins. Moreover, the increased frequency of aromatic amino acids in thermophilic proteins contributes to thermal stability by forming more aromatic interactions. Additionally, the coil, helix, and loop in the secondary structure also contribute to thermostability.

Altering the substrate specificity of recombinant l-rhamnose isomerase from Thermoanaerobacterium saccharolyticum NTOU1 to favor d-allose production

l-Rhamnose isomerase (l-RhI) catalyzes rare sugar isomerization between aldoses and ketoses. In an attempt to alter the substrate specificity of Thermoanaerobacterium saccharolyticus NTOU1 l-RhI (TsRhI), residue Ile102 was changed to other polar or charged amino acid residues by site-directed mutagenesis. The results of activity-screening using different substrates indicate that I102N, I102Q, and I102R TsRhIs can increase the preference against d-allose in comparison with the wild-type enzyme. The catalytic efficiencies of the purified I102N, I102Q, and I102R TsRhIs against d-allose are 148 %, 277 %, and 191 %, respectively, of that of wild-type enzyme, while those against l-rhamnose are 100 %, 167 % and 87 %, respectively. Mutant I102N, I102Q, and I102R TsRhIs were noted to have the altered substrate specificity, and I102Q TsRhI has the highest catalytic efficiency against d-allose presumably through the formation of an additional hydrogen bond with d-allose. The purified wild-type and mutant TsRhIs were further used to produce d-allose from 100 g/L d-fructose in the presence of d-allulose 3-epimerase, and the yields can reach as high as 22 % d-allulose and 12 % d-allose upon equilibrium. I102Q TsRhI takes only around half of the time to reach the same 12 % d-allose yield, suggesting that this mutant enzyme has a potential to be applied in d-allose production.

A proteome-scale analysis of vertebrate protein amino acid occurrence: Thermoadaptation shows a correlation with protein solvation but less so with dynamics.

Despite differences in behaviors and living conditions, vertebrate organisms share the great majority of proteins, often with subtle differences in amino acid sequence. Here, we present a simple way to analyze the difference in amino acid occurrence by comparing highly homologous proteins on a subproteome level between several vertebrate model organisms. Specifically, we use this method to identify a pattern of amino acid conservation as well as a shift in amino acid occurrence between homeotherms (warm-blooded species) and poikilotherms (cold-blooded species). Importantly, this general analysis and a specific example further establish a broad correlation, if not likely connection between the thermal adaptation of protein sequences and two of their physical features: on average a change in their protein dynamics and, even more strongly, in their solvation. For poikilotherms, such as frog and fish, the lower body temperature is expected to increase the protein-protein interaction due to a decrease in protein internal dynamics. In order to counteract the tendency for enhanced binding caused by low temperatures, poikilotherms enhance the solvation of their proteins by favoring polar amino acids. This feature appears to dominate over possible changes in dynamics for some proteins. The results suggest that a general trend for amino acid choice is part of the mechanism for thermoadaptation of vertebrate organisms at the molecular level.

P-099: ANTI-SICKLING STUDY OF THE AQUEOUS EXTRACTS OF TINOSPORA CARDIFOLIA AND TERMINALIA BELLIRICA

Purpose: Introduction: - Sickle cell anaemia also known as drepanocytosis, is a genetic blood related disease in which red blood cells form an cresent (sickle) or abnormal shape. This genetic disease is due to a change in the beta globin chain of haemoglobin glutamic acid (a polar amino acid) is replaced by valine (a non – polar) amino acid. This genetical change reduces the binding of haemoglobin for oxygen. At the low oxygen level the mutant haemoglobin, known as sickle haemoglobin (Hbss). Medicinal plants have been used in Indian folk medicine in the remedy of sickle cell anaemia by inhibiting sickling. This work was therefore aimed at screening the antisickling study of the aqueous extract of stems of T. Cardifolia and fruits of T.bellirica used in the Indian herbal medicine. Objective:- The present study investigates the preliminary screening of secondary metabolites of aqueous extracts of T. Cardifolia(stems) and T.bellirica(fruits) and invitro antisickling test (sickling reversal test). Materials and methods: Standard methods of phytochemical analysis of T. Cardifolia(stems) and T.bellirica(fruits) and sickling reversal test (invitro antisickling test), stems of T. Cardifolia,fruits of T.bellirica and Hbss blood samples etc. Results: Screening of secondary metabolites (bioactive molecules) and sickling reversal test were carried out using standard methods. The phyto-chemical screening indicated the presence of secondary metabolites (bioactive molecules) viz - alkaloids,flavonoids,phenols, saponins, steroids and cardiac glycosides etc. The results of antisickling reversal test that T. cardifolia(stems) and T. bellirica (fruits) exhibited potential antisickling property. Conclusion: The percentage of sickle cells of untreated Hbss was statistically significant higher than treated Hbss. The percentage of sickle cells decreased on the addition of aqueous extract of T. cardifolia stems and T. bellirica fruits on induced Hbss blood, which indicates the reversal of of Hbss blood to normal biconcave shape due to the presence of bioactive molecules, which have sickling reversal (anti-sickling property) and anti haemolytic properties. The authors do not declare any conflict of interest

Biomimetic Mineralization of Tooth Enamel Using Nanocrystalline Hydroxyapatite under Various Dental Surface Pretreatment Conditions.

In this report, we demonstrated the formation of a biomimetic mineralizing layer obtained on the surface of dental enamel (biotemplate) using bioinspired nanocrystalline carbonate-substituted calcium hydroxyapatite (ncHAp), whose physical and chemical properties are closest to the natural apatite dental matrix, together with a complex of polyfunctional organic and polar amino acids. Using a set of structural, spectroscopy, and advanced microscopy techniques, we confirmed the formation of a nanosized ncHAp-based mineralized layer, as well as studying its chemical, substructural, and morphological features by means of various methods for the pretreatment of dental enamel. The pretreatment of a biotemplate in an alkaline solution of Ca(OH)2 and an amino acid booster, together with the executed subsequent mineralization with ncHAp, led to the formation of a mineralized layer with homogeneous micromorphology and the preferential orientation of the ncHAp nanocrystals. It was shown that the homogeneous crystallization of hydroxyapatite on the biotemplate surface and binding of individual nanocrystals and agglomerates into a single complex by an amino acid booster resulted in an increase (~15%) in the nanohardness value in the enamel rods area, compared to that of healthy natural enamel. Obtaining a similar hierarchy and cleavage characteristics as natural enamel in the mineralized layer, taking into account the micromorphological features of dental tissue, is an urgent problem for future research.

Impacts of perfluorooctanesulfonic acid on plant biometrics and grain metabolomics of wheat (Triticum aestivum L.)

Per- and polyfluoroalkyl substances (PFAS) are utility chemicals that have become environmental contaminants of global concern due to their bioaccumulative and persistent nature. The accumulation and effects of perfluorooctanesulfonic acid (PFOS), a type of PFAS, on agricultural plants is a serious environmental concern that needs to be investigated. Wheat was exposed to soil amended with 0, 25, and 50 mg/kg PFOS and assessed for PFOS’ impacts via agronomic measurements, biochemical assays, PFOS uptake, and ionomics and metabolomics analyses over the lifetime of the plant. PFOS was taken up in the roots and relocated to the grains, which accumulated PFOS at levels 12-18 times higher in treated plants than in control. Compared to control, 50 mg/kg PFOS reduced chlorophyll content by 49% and root biomass by 37% early on during the exposure. At the end of full life cycle exposure, PFOS did not affect the agronomic and productivity status of plants. However, PFOS impacted grain quality by reducing concentrations of macroelements (Mg, K, and P) and levels of important sugar metabolites (e.g., sucrose, glucose 6-phosphate, fructose 6-phosphate, trehalose). PFOS also decreased the abundance of non-polar proteinogenic amino acids but increased the levels of polar amino acids in grains. These findings highlight impacts of PFOS on an important agronomic crop.

Synthesis, molecular modeling and antioxidant screening of new thioether-bridged thiadiazole and thiadiazolopyrimidine analogues

The N-aryl-2-((5-(2-cyanoacetamido)-1,3,4-thiadiazol-2-yl)thio)acetamide derivatives 3a-c were prepared and successfully reacted with N,N-dimethylformamide dimethyl acetal (DMF-DMA). The resulting N-thiadiazolyl-2-cyano-3-(dimethylamino)acrylamide derivatives 4a-c were cyclized in boiling acetic acid to yield the corresponding thiadiazolopyrimidine compounds 5a-c. The structural properties of synthesized compounds were studied using DFT/B3LYP level. The HOMO-LUMO energies were employed in determination of some chemical reactivity descriptors. Despite the close energy gap values (ΔEH-L) of the investigated compounds, the data showed that chloro derivatives has the highest energy gap while the methoxy derivatives were the lowest. The synthesized compounds were investigated to explore their antioxidant activities. The results showed that the N-thiadiazolyl-2-cyano-3-(dimethylamino)acrylamides 4a-c had higher inhibition IC50 values (24.27–31.64 µg/mL) than the thiadiazolyl cyanoacetamides 3a-c (34.26–39.33 µg/mL). However, thiadiazolopyrimidines 5a-c presented moderate inhibition with (IC50 = 40.21–44.19 µg/mL) in comparison to ascorbic acid and BHT (Butylated hydroxytoluene) as reference drugs with IC50 = 22.66 and 27.24 µg/mL, respectively. Furthermore, the synthesized compounds were evaluated against (PDB Code-3ML5) using the MOE operation v10.2015.10 database. The inspected synthesized thiadiazole derivatives 3, 4 and 5 revealed H-bond linkages over the receptor through the disparate polar amino acids (Thr 200, Thr 199, Gln 67, His 94, and Lys 91) of larger pocket size of 3ML5. The results of the docking study presented a remarkable agreement with the practical results of the antioxidant activity.

Interactions of boron nitride nanosheet with amino acids of differential polarity

Free amino acids represent a category of different biomolecules in the blood plasma, which bond together to make up larger organic molecules such as peptides and proteins. Their interactions with biocompatible nanoparticles are especially important for plasma-related biomedical applications. Among the various nanomaterials, the applications of carbon and boron nitride-based nanotubes/nanosheets have shown a huge increase in recent years. The effect of molecular polarity on the interaction between a boron nitride nanosheet (BNNS) and amino acids is investigated with quantum mechanical calculations by density functional theory (DFT), classical MD simulations, and well-tempered metadynamics simulations. Four representative amino acids, namely, alanine (Ala), a nonpolar amino acid, and aspartic acid (Asp), lysine (Lys) and serine (Ser), three polar amino acids are considered for their interactions with BNNS. In DFT calculations, the values of the adsorption energies for Lys-BNNS and Ser-BNNS complexes are − 48.32 and − 32.89 kJ/mol, respectively, which are more stable than the other cases. Besides, the adsorption energy calculated confirms the exergonic reactions for all investigated systems; it implied that the interaction is favorable electronically. The MD results show that the LYS molecules have a higher attraction toward BNNS because of its alkane tail in its side chain, and the ASP revealed the repulsion force originating from its COO– group. All the results are confirmed by free energy analyzes in which the LYS showed the highest adsorption free energy at a relatively farther distance than other complexes. In fact, our results revealed the contribution of functional groups and backbone of the amino acids in the adsorption or repulsion features of the studied systems.

Respiratory complex I with charge symmetry in the membrane arm pumps protons

Energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, is essential for cellular energy metabolism coupling NADH oxidation to proton translocation. The mechanism of proton translocation by complex I is still under debate. Its membrane arm contains an unusual central axis of polar and charged amino acid residues connecting the quinone binding site with the antiporter-type subunits NuoL, NuoM, and NuoN, proposed to catalyze proton translocation. Quinone chemistry probably causes conformational changes and electrostatic interactions that are propagated through these subunits by a conserved pattern of predominantly lysine, histidine, and glutamate residues. These conserved residues are thought to transfer protons along and across the membrane arm. The distinct charge distribution in the membrane arm is a prerequisite for proton translocation. Remarkably, the central subunit NuoM contains a conserved glutamate residue in a position that is taken by a lysine residue in the two other antiporter-type subunits. It was proposed that this charge asymmetry is essential for proton translocation, as it should enable NuoM to operate asynchronously with NuoL and NuoN. Accordingly, we exchanged the conserved glutamate in NuoM for a lysine residue, introducing charge symmetry in the membrane arm. The stably assembled variant pumps protons across the membrane, but with a diminished H+/e- stoichiometry of 1.5. Thus, charge asymmetry is not essential for proton translocation by complex I, casting doubts on the suggestion of an asynchronous operation of NuoL, NuoM, and NuoN. Furthermore, our data emphasize the importance of a balanced charge distribution in the protein for directional proton transfer.

Effects of zein modifying polar amino acids as surface stabilizers on the emulsification stability of milk cream diacylglycerol

It is important to improve the emulsification stability of oil-in-water emulsions by surface loading hydrophilic groups. l-Glutamic acid (Glu), l-Glutamine (Gln) and l-Arginine (Arg) were used to modify Zein-Chitosan lactate (CHL) as stabilizers to improve the emulsification stability of milk cream diacylglycerol (DAG). The mechanism of using polar amino acids to enhance the emulsification of DAG-in-water emulsion was explored. The results showed that the average droplet size of DAG emulsion was 48 μm by using Zein-CHL-Gln as surface stabilizer when the pH was 6.0, and the ratio of Gln and CHL was 1:1. Zein-CHL-Gln as surface stabilizer could improve the emulsion index by 25% compared with the control group after storage for 7 days. Hydrophobic interaction between L-Gln and zein played an important role in increasing the hydrophilic polar moiety on the emulsion surface. Zein-CHL modified with l-Glutamine was better surface stabilizer to improve the emulsification of oil-in-water emulsions.

The intrinsically disordered region from PP2C phosphatases functions as a conserved CO2 sensor.

Carbon dioxide not only plays a central role in the carbon cycle, but also acts as a crucial signal in living cells. Adaptation to changing CO2 concentrations is critical for all organisms. Conversion of CO2 to HCO3- by carbonic anhydrase and subsequent HCO3--triggered signalling are thought to be important for cellular responses to CO2 (refs. 1-3). However, carbonic anhydrases are suggested to transduce a change in CO2 rather than be a direct CO2 sensor4,5, the mechanism(s) by which organisms sense CO2 remain unknown. Here we demonstrate that a unique group of PP2C phosphatases from fungi and plants senses CO2, but not HCO3-, to control diverse cellular programmes. Different from other phosphatases, these PP2Cs all have an intrinsically disordered region (IDR). They formed reversible liquid-like droplets through phase separation both in cells and in vitro, and were activated in response to elevated environmental CO2 in an IDR-dependent manner. The IDRs in PP2Cs are characterized by a sequence of polar amino acids enriched in serine/threonine, which provides CO2 responsiveness. CO2-responsive activation of PP2Cs via the serine/threonine-rich IDR-mediated phase separation represents a direct CO2 sensing mechanism and is widely exploited.