SS Formation Research Articles

Cooking mediated wheat gluten aggregation behavior: Physicochemical properties and component changes

Changes in the physicochemical properties of wheat gluten (WG) during cooking are mainly dependent on its intramolecular and intermolecular interactions when subjected to high-temperature treatment. In this study, the effects and mechanisms of cooking on the aggregation behavior of WG were investigated. Results showed that an increase in cooking time led to an initial increase and subsequent decrease in WG viscoelasticity, with optimal viscoelastic properties observed at 5 min. As cooking proceeded, covalent cross-linking of WG deepened and the contribution of hydrogen bonds to maintaining WG structure weakened, while the contribution of hydrophobic interactions strengthened. Cooking increased the proportion of gauche-gauche-gauche in the disulfide (SS) bridge conformation and decreased the homogeneity of the WG network. The unfolding of gluten molecules caused by hydrogen bonds breaking and intermolecular cross-linking through hydrophobic interactions and SS formation jointly contributing to the rheological properties of WG. Notably, glutenin (Glu) exhibited more similar physicochemical changes to WG during cooking than gliadin (Gli). Glu was more sensitive to cooking than Gli and formed dense, continuous aggregates prior to Gli. Cross-links formed by Glu occupied the majority of three-dimensional network of WG, while Gli was involved only in the form of branched chains. This may explain why Glu dominates the physicochemical changes of WG during cooking. This study contributes to a deeper understanding of the thermal denaturation mechanism of WG and provides new insights into the processing of flour-based foods.

Effects of Early Pollution Control Measures on Secondary Species of PM2.5 in Jiaozuo, China.

Various measures for reducing air pollution have been promulgated since 2013 in China. To investigate the synergistic results of emission control and meteorological environment, PM2.5 samples collected from October 2013 to July 2016 and November 2018 to October 2019 in Jiaozuo city were analyzed for their compositions, secondary species (Ss) variations, and factors changing for Ss formation. The results showed that the concentrations of sulfate, nitrate, ammonium, and secondary organic aerosols (SOAs) generally decreased over the same seasonal period during these years. In addition, the concentrations and proportions of each Ss increased with the increase in the PM2.5 level in these years, implying that although PM2.5 levels have been reduced by various control policies, Ss formation would remain the major contributor to PM elevations. The enhanced effects of gas-phase reactions on intensification of sulfate, SOA, and PM were observed in 2018–2019, which was consistent with the elevation of nitrate and SOA at PM levels of >150 μg/m3. Only sulfate in all PM levels sharply decreased after 2015, showing the fine effect of coal-related pollution control and the importance of collaborative control of NOx, volatile organic compounds, and organic aerosol emissions with SO2 emissions in the future.

Dynamic thiol-disulfide balance in patients with chronic sinusitis with and without nasal polyposis

Aim: Reactive oxygen species (ROS) have a crucial role in the pathogenesis of chronic rhinosinusitis (CRS). The current study investigates a novel oxidative stress marker (thiol (SH)/disulfide (SS) homeostasis) in patients with CRS with and without nasal polyposis (NPs).Materials and Methods: A total of 167 subjects, including 94 patients with CRS and 73 healthy controls, were included in the study. The patients were subdivided into two groups those with CRS with NP and those with CRS without NP. Comparisons were made between the groups in respect of serum native SH, total thiol (TT), and SS levels and the SS/SH and SS/TT ratios. Results: There was no significant difference in TT between the CRS with the NP group and the CRS without the NP group (p> 0.05). There was a significant difference (p 0.05) between the CRS without the NP group and the control group in %SH/TT, %SS/TT, %SS/SH, SS, and SH. A significant difference (p 0.05) was found between the CRS with the NP group and the control group in %SH/TT, %SS/TT, %SS/SH, SS and SH values. Conclusion: Dynamic SH/SS homeostasis shifts towards SS formation as a result of SH oxidation in patients with CRS.

Powstanie kawalerii SS Totenkopf i jej rola w niemieckiej polityce okupacyjnej na ziemiach polskich w latach 1939–1941

The topic of the article is one of the German SS regiments stationed in occupied Poland and its role in The German occupation policy. While the history of the SS formation is very well known in both academic and popular science literature, its cavalry has not been elaborated in great detail thus far. Although this topic seems interesting, it has not yet been discussed in any book in the Polish language. Most of the literature related to this topic was published in German and English. The 1st SS Death’s Head Cavalry Regiment operated primarily in the General Government and was under the Higher SS and Police Command. Some of its squadrons also operated in areas annexed to the Reich, i.e. the Warta Voievodship (Reichsgau Wartheland). From this article we will learn about the formation of the SS Death’s Head cavalry and its gradual inclusion in the brutal occupation policy of the Third Reich in Poland. In the case of its formation, we are dealing with tasks such as combating the early partisan units, searching for weapons, participating in the creation of ghettos, or helping to eliminate Polish levels of the intelligentsia. Noteworthy is the participation of this unit in the production of the propaganda film “Kampfgeschwader Lützow”, in which Polish cavalrymen were presented attacking German tanks with sabres. This false image was reproduced after the war in some movies or books, and contributed to the distorted presentation of Polish soldiers in the defensive battles of 1939.

Transition-metal-free PhI(OAc)2-mediated oxidative S[sbnd]S and C[sbnd]N bond formation: Regioselective synthesis of 3H-1,2,4-dithiazol-3-imines

An effective and new approach is proposed for the synthesis of regioselective 3H-1,2,4-dithiazol-3-imines through SS and CN bond formation for the first time from benzothioamides and isothiocyanates under transition-metal-free conditions. This protocol proceeds by using hypervalent iodine(III) compound of phenyliodine diacetate (PhI(OAc)2) having additive cesium carbonate in acetonitrile solution at room temperature to provide facile access to 3H-1,2,4-dithiazol-3-imine derivatives from readily available starting materials with broad substrate scope, insensitive to air and moisture, regioselectivity and affluent up to gram scale.

Oxidative folding pathways of bovine milk β-lactoglobulin with odd cysteine residues.

Bovine β‐lactoglobulin (BLG) is a major whey protein with unique structural characteristics: it possesses a free Cys thiol (SH) and two disulfide (SS) bonds and consists of a β‐barrel core surrounded by one long and several short α helices. Although SS‐intact conformational folding has been studied in depth, the oxidative folding pathways and accompanying SS formation/rearrangement are poorly understood. In this study, we used trans‐3,4‐dihydroxyselenolane oxide, a water‐soluble selenoxide reagent which undergoes rapid and quantitative SS formation, to determine the oxidative folding pathways of BLG variant A (BLGA) at pH 8.0 and 25 °C. This was done by characterizing two key one‐SS intermediates, a particular folding intermediate having a Cys66–Cys160 SS bond (I‐1) and a particular folding intermediate having a Cys106–Cys119 SS bond (I‐2), which have a native Cys66–Cys160 and Cys106–Cys119 SS bond, respectively. In the major folding pathway, the reduced protein (R) with abundant α helices was oxidized to I‐1, which was then transformed to I‐2 through SS rearrangement. The native protein (N) was formed by oxidation of I‐2. The redundant Cys121 thiol facilitates SS rearrangement. N is also generated from an ensemble of folding intermediates having two SS bonds (2SS) intermediates with scrambled SS bonds through SS rearrangement, but this minor pathway is deteriorative due to aggregation or overoxidation of 2SS. During oxidative folding of BLGA, α→β conformational transition occurred as previously observed in SS‐intact folding. These findings are informative not only for elucidating oxidative folding pathways of other members of the β‐lactoglobulin family, but also for understanding the roles of a redundant Cys thiol in the oxidative folding process of a protein with odd Cys residues.

Effects of Metal Ions, Temperature, and a Denaturant on the Oxidative Folding Pathways of Bovine α-Lactalbumin.

Bovine α-lactalbumin (αLA) has four disulfide (SS) bonds in the native form (N). On the oxidative folding pathways of this protein, two specific SS folding intermediates, i.e., (61–77, 73–91) and des[6–120], which have two and three native SS bonds, respectively, accumulate predominantly in the presence of Ca2+. In this study, we reinvestigated the pathways using a water-soluble cyclic selenoxide reagent, trans-3,4-dihydroxyselenolane oxide (DHSox), as a strong and quantitative oxidant to oxidize the fully reduced form (R). In the presence of ethylenediaminetetraacetic acid (EDTA) (under a metal-free condition), SS formation randomly proceeded, and N did not regenerate. On the other hand, two specific SS intermediates transiently generated in the presence of Ca2+. These intermediates could be assigned to (61–77, 73–91) and des[6–120] having two common SS bonds, i.e., Cys61-Cys77 and Cys73-Cys91, near the calcium binding pocket of the β-sheet domain. Much faster folding to N was observed in the presence of Mn2+, whereas Na+, K+, Mg2+, and Zn2+ did not affect the pathways. The two key intermediates were susceptible to temperature and a denaturant. The oxidative folding pathways revealed were significantly different from those of hen egg white lysozyme, which has the same SS-bonding pattern as αLA, suggesting that the folding pathways of SS-containing proteins can alter depending on the amino acid sequence and other factors, even when the SS-bond topologies are similar to each other.

An amphiphilic selenide catalyst behaves like a hybrid mimic of protein disulfide isomerase and glutathione peroxidase 7.

Protein disulfide isomerase (PDI) and glutathione peroxidase 7 (GPx7) cooperatively promote the oxidative folding of disulfide (SS)-containing proteins in endoplasmic reticulum by recognizing the nascent proteins to convert them into the native folds by means of SS formation and SS isomerization and by catalyzing reoxidation of reduced PDI with H2O2, respectively. In this study, new amphiphilic selenides with a long-chain alkyl group were designed as hybrid mimics of PDI and GPx7 and were applied to the refolding of reduced hen egg-white lysozyme (HEL-R). Competitive SS formation at pH 4 using HEL-R and glutathione (GSH) in the presence of the selenide catalyst and H2O2 showed that the amphiphilic selenides can preferentially catalyze SS formation of HEL-R, probably on account of hydrophobic interactions between the protein and the catalyst. In contrast, simple water-soluble selenides did not exhibit such behavior. In addition, when the pH of the solution was adjusted to 8.5 after the SS formation, surviving GSH promoted the SS isomerization of misfolded HEL to recover the native SS linkages. Thus, the amphiphilic selenides designed here could mimic the function of the PDI-GPx7 system. The combination of a water-soluble selenide and a long-chain alkyl group would be a useful motif in designing medicines for both protein misfolding diseases and antioxidant therapy.

A water-soluble selenoxide reagent as a useful probe for the reactivity and folding of polythiol peptides

A water-soluble selenoxide (DHSox) having a five-membered ring structure enables rapid and selective conversion of cysteinyl SH groups in a polypeptide chain into SS bonds in a wide pH and temperature range. It was previously demonstrated that the second-order rate constants for the SS formation with DHSox would be proportional to the number of the free SH groups present in the substrate if there is no steric congestion around the SH groups. In the present study, kinetics of the SS formation with DHSox was extensively studied at pH 4–10 and 25 °C by using reduced ribonuclease A, recombinant hirudin variant (CX-397), insulin A- and B-chains, and relaxin A-chain, which have two to eight cysteine residues, as polythiol substrates. The obtained rate constants showed stochastic SS formation behaviors under most conditions. However, the rate constants for CX-397 at pH 8.0 and 10.0 were not proportional to the number of the free SH groups, suggesting that the SS intermediate ensembles possess densely packed structures under weakly basic conditions. The high two-electron redox potential of DHSox (375 mV at 25 °C) compared to l-cystine supported the high ability of DHSox for SS formation in a polypeptide chain. Interestingly, the rate constants of the SS formation jumped up at a pH around the pKa value of the cysteinyl SH groups. The SS formation velocity was slightly decreased by addition of a denaturant due probably to the interaction between the denaturant and the peptide. The stochastic behaviors as well as the absolute values of the second-order rate constants in comparison to dithiothreitol (DTTred) are useful to probe the chemical reactivity and conformation, hence the folding, of polypeptide chains.

Kinetic and thermodynamic analysis of the conformational folding process of SS-reduced bovine pancreatic ribonuclease A using a selenoxide reagent with high oxidizing ability

Redox-coupled folding pathways of bovine pancreatic ribonuclease A (RNase A) with four intramolecular disulfide (SS) bonds comprise three phases: (I) SS formation to generate partially oxidized intermediate ensembles with no rigid folded structure; (II) SS rearrangement from the three SS intermediate ensemble (3S) to the des intermediates having three native SS linkages; (III) final oxidation of the last native SS linkage to generate native RNase A. We previously demonstrated that DHSox, a water-soluble selenoxide reagent for rapid and quantitative SS formation, allows clear separation of the three folding phases. In this study, the main conformational folding phase (phase II) has been extensively analyzed at pH 8.0 under a wide range of temperatures (5–45°C), and thermodynamic and kinetic parameters for the four des intermediates were determined. The free-energy differences (ΔG) as a function of temperature suggested that the each SS linkage has different thermodynamic and kinetic roles in stability of the native structure. On the other hand, comparison of the rate constants and the activation energies for 3S→des with those reported for the conformational folding of SS-intact RNase A suggested that unfolded des species (desU) having three native SS linkages but not yet being folded are involved in very small amounts (<1%) in the 3S intermediate ensemble and the desU species would gain the native-like structures via X-Pro isomerization like SS-intact RNase A. It was revealed that DHSox is useful for kinetic and thermodynamic analysis of the conformational folding process on the oxidative folding pathways of SS-reduced proteins.

Rapid and Quantitative Disulfide Bond Formation for a Polypeptide Chain Using a Cyclic Selenoxide Reagent in an Aqueous Medium

To elucidate the reaction mechanism of the disulfide (SS) bond formation reaction of a polypeptide molecule with a water-soluble selenoxide reagent, trans-3,4-dihydroxyselenolane oxide (DHS(ox)), short-term oxidation experiments were carried out for the reduced state (R) of a recombinant hirudin CX-397 variant at pH 7.0 and 25 °C. In the reaction, R was oxidized sequentially to one-SS, two-SS, and three-SS intermediate ensembles within 1 min. The kinetic analysis revealed that the three second-order rate constants for the SS formation are proportional to the number of thiol groups existing in the reactant SS intermediates, indicating the stochastic nature of the SS formation. Ab initio calculation at the HF/6-31++G(d,p) level in water by using the polarizable continuum model suggested that the SS formation reaction is highly exothermic and proceeds via a reactive thioselenurane intermediate with a distorted linear O-Se-S linkage. The results clearly demonstrated that the rate-determining step of the SS formation reaction is the first bimolecular process between a thiol substrate and DHS(ox) rather than the subsequent process to release a SS product.

Characterization of Kinetic and Thermodynamic Phases in the Prefolding Process of Bovine Pancreatic Ribonuclease A Coupled with Fast SS Formation and SS Reshuffling

In the redox-coupled oxidative folding of a protein having several SS bonds, two folding phases are usually observed, corresponding to SS formation (oxidation) with generation of weakly stabilized heterogeneous structures (a chain-entropy losing phase) and the subsequent intramolecular SS rearrangement to search for the native SS linkages (a conformational folding phase). By taking advantage of DHS(ox) as a highly strong and selective oxidant, the former SS formation phase was investigated in detail in the oxidative folding of RNase A. The folding intermediates obtained at 25 °C and pH 4.0 within 1 min (1S°-4S°) showed different profiles in the HPLC chromatograms from those of the intermediates obtained at pH 7.0 and 10.0 (1S-4S). However, upon prolonged incubation at pH 4.0 the profiles of 1S°-3S° transformed slowly to those similar to 1S-3S intermediate ensembles via intramolecular SS reshuffling, accompanying significant changes in the UV and fluorescence spectra but not in the CD spectrum. Similar conversion of the intermediates was observed by pH jump from 4.0 to 8.0, while the opposite conversion from 1S-4S was observed by addition of guanidine hydrochloride to the folding solution at pH 8.0. The results demonstrated that the preconformational folding phase coupled with SS formation can be divided into two distinct subphases, a kinetic (or stochastic) SS formation phase and a thermodynamic SS reshuffling phase. The transition from kinetically formed to thermodynamically stabilized SS intermediates would be induced by hydrophobic nucleation as well as generation of the native interactions.

Functional properties and in vitro trypsin digestibility of red kidney bean (Phaseolus vulgaris L.) protein isolate: Effect of high-pressure treatment

The effects of high-pressure (HP) treatment at 200–600MPa, prior to freeze-drying, on some functional properties and in vitro trypsin digestibility of vicilin-rich red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) were investigated. Surface hydrophobicity and free sulfhydryl (SH) and disulfide bond (SS) contents were also evaluated. HP treatment resulted in gradual unfolding of protein structure, as evidenced by gradual increases in fluorescence strength and SS formation from SH groups, and decrease in denaturation enthalpy change. The protein solubility of KPI was significantly improved at pressures of 400MPa or higher, possibly due to formation of soluble aggregate from insoluble precipitate. HP treatment at 200 and 400MPa significantly increased emulsifying activity index (EAI) and emulsion stability index (ESI); however, EAI was significantly decreased at 600MPa (relative to untreated KPI). The thermal stability of the vicilin component was not affected by HP treatment. Additionally, in vitro trypsin digestibility of KPI was decreased only at a pressure above 200MPa and for long incubation time (e.g., 120min). The data suggest that some physiochemical and functional properties of vicilin-rich kidney proteins can be improved by means of high-pressure treatment.

On the formation mechanism of BaTiO 3–BaZrO 3 solid solution through solid-oxide reaction

The formation of solid solution composition BaTi 0.6Zr 0.4O 3, from BaCO 3, TiO 2 and ZrO 2 powders has been studied through solid-oxide reaction using TGA/DSC, XRD. BaCO 3 decomposes at much lower temperature in the mixture due to the presence of TiO 2. BaTiO 3 (BT) and BaZrO 3 (BZ) start forming from the temperature range 700–800 °C without intermediate formation of BaO or other titanate/zirconate phases. Rate of BaTiO 3 formation is higher than BaZrO 3 formation due to the lower activation energy (34.3 kcal/mol) required for titanate formation than zirconate (48.4 kcal/mol). Solid solution then forms by diffusion of BaTiO 3 into BaZrO 3 from 1300 °C onwards. Lattice parameter of initial SS phase is higher, indicating the phase has a coherent interface with zirconate and higher in Zr-concentration than the final product. Activation energy for the SS formation (133 kcal/mol) indicates that Ba and/or O diffusion through SS layer may limit the reaction.

Determination of hydrophobicity and reactive groups in proteins of cod ( Gadus morhua) muscle during frozen storage

This study, to elucidate the possible sources of protein denaturation and cross-linkage which cause textural deterioration, was a continuation of our work on the same lot of commercially harvested and processed fillets of Northern bank trawl cod ( Gadus morhua), frozen stored for ca. 300 days at −30°C, −22°C, −15°C, −12°C and under conditions of fluctuating temperatures simulating industrial practice. Sarcoplasmic, myosin-rich and SDS-soluble protein fractions from each treatment were evaluated for surface hydrophobicity, total, available and unavailable SH, SS, aldehydes, free NH2 and ester-link content. Changes in surface hydrophobicity in the three fractions may be caused by increases in SS bonding, ester-links, aldehydes and free NH2 groups. These results demonstrate that hydrophobicity is not only attributed to SS formation but also to ester-links, aldehydes and free NH2 groups.

Structural and kinematic evolution of the teslin suture zone, Yukon: record of an ancient transpressional margin

The Teslin suture zone (TSZ), Yukon, which forms the fundamental boundary between rocks deposited along the ancient margin of North America, and allochthonous terranes to the west, preserves a complex history of pre-mid-Jurassic convergence and dextral strike-slip translation which is overprinted locally by late Cretaceous dextral strike-slip shear. The TSZ, comprised of a 15–20 km thick structural sequence of ductilely deformed sedimentary and volcanic strata, basalt, peridotite and granitoids, is divisible into distinct elongate structural domains based on the distribution of two well-defined but differently oriented stretching lineations, L ds and L ss, L ds and L ss both formed during non-coaxial ductile deformation; L ds trends E-W and plunges down-dip, whereas L ss trends NNW-SSE and plunges shallowly. Two 1–2 km wide, NNW-trending anastomosing shear zones of L ss cross-cut L ds structures, indicating L ss is younger. Other field relations indicate further that L ds began forming earlier than L ss, followed by a period of coeval L ds and L ss formation; latest motion was dominantly parallel to L ss. Synkinematic mineral assemblages associated with both L ds- and L ss-related structures record greenschist to albite-epidote amphibolite facies conditions. L ds tectonites record a complex movement history: to the west textural asymmetries indicate west-side-down, or normal shear, whereas in eastern domains top-to-the-east thrust-style asymmetries dominate. L ss tectonites consistently record dextral, or top-to-the-north, shear parallel to L ss. Tectonic motion began as chiefly penetrative dip-slip shear ( L ds) at a high angle to the present trend of the TSZ, and evolved to dominantly dextral strike-slip shear ( L ss) parallel to the trend of the zone. The geometry, kinematics and sequence of deformation in TSZ tectonites evoke a general model of terrane accretion during oblique plate convergence involving initial shortening at a high angle to the convergent margin and progression to margin-parallel translation.

The role of titania and titania mixtures in the nucleation and crystallization of spodumene—willemite—diopside glasses

The nucleation and crystallization processes in glasses and melts of different compositions within the system spodumene—willemite—diopside, using different proportions of TiO 2 and mixtures of TiO 2+ZrO 2 and TiO 2+ZrO 2+F as nucleating agents, have been studied by employing a combination of DTA, X-ray diffraction, and optical and scanning electron microscopy. Incorporation of titania or its mixtures in the base composition modified the crystallization kinetics, as expressed by variations observed on the peak temperatures and spans of the DTA exotherms of crystallization. These nucleants also influenced the type and relative proportions of the crystallized phases, transformation temperatures, degree of metastability of β-Zn 2SiO 4 and β-eucryptite ss 1 1 ss=solid solution; β-eucryptite ss was also named β-quartz ss in the literature. , and the texture of the resultant glass-ceramic. TiO 2 additions lowered the onset crystallization temperatures and favoured the crystallizability. TiO 2 catalyzed the pyroxene and β-eucryptite ss formation and also the transformation of the latter into β-spodumene ss. TiO 2+ZrO 2 mixtures enhanced the crystallization but retarded phase transformation. Addition of F to TiO 2+ZrO 2 showed a synergistic effect to the action of TiO 2 and also greatly facilitated willemite formation. The proposed nucleation mechanism of titania and its mixtures involves the enhancement of liquid-liquid phase separation followed by the separation of a zinc titanate phase which heterogeneously nucleates the crystallization of the glass bulk.

Studies on the relationship of disulfide bonds to the formation and maintenance of secondary structure in chicken egg white lysozyme.

The dependence of secondary structure on SS content was examined to gain further insight into the role of SS bond formation in chain folding. Lysozyme was reduced to various levels, and the products were studied with respect to remaining native structure. Reductions were carried out in the absence of denaturant. Thus, the observed changes were not attributable to a general denaturing effect, but more specifically to cleavage of SS bonds. The products of reduction were found by gel filtration chromatography to contain both polymeric and monomeric forms. By "fingerprinting", the monomers gave no indication of having undergone SS interchange, and specific cleavage of native SS bonds was indicated by a stepwise disappearance of SS-containing peptides with increasing reduction level. Ion-exchange chromatography of the carboxymethylated monomers gave the three possible reduction intermediates, containing two, four, and six carboxymethylcysteine residues per mole, in addition to the fully reduced form. The intermediates exhibited circular dichroic (CD) characteristics that were clearly nonnative, indicating alteration of the secondary structure throughout all stages of reduction. Concomitantly, there were extensive losses of enzymatic activity at intermediate levels, while no activity was found for the fully reduced form. Partially and fully reduced lysozymes were also examined for their abilities to resume native secondary structure in the absence of SS formation, as would be evidenced by a reversion to native CD characteristics. Despite literature indications of native structure in the reduced protein as observed from examination of CD behavior, none was found in the present effort, under a variety of experimental conditions. These observations are consistent with an essential role of SS bonds in forming and maintaining a major portion of the native secondary structure in lysozyme.

The effect of sulfhydryl reagents on freezing resistance of hardened and unhardened cabbage cells

Summary Pretreatment of cabbage sections with nontoxic concentrations of the sulfhydryl reagents PCMB or IA decreased their resistance to freezing injury. Thiols had no effect. As the plants hardened, the SH reagents produced less and less of a decrease in their resistance to freezing injury. This result is explained by a decrease in or protection of protein SH. The decrease in freezing resistance is the opposite of what would be predicted by the SH hypothesis of freezing injury, if the SH reagents simply prevent intermolecular SS formation, but other evidence indicates that they also induce some protein unfolding. It is proposed that this unfolding favors the aggregation of proteins on freezing.

The effect of cryoprotective agents on intermolecular SS formation during freezing of Thiogel

Summary Both cryoprotective agents (glycerol and dimethyl sulfoxide) and substances of little (sucrose) or no (urea and NaCl) protective value in living cells, retard intermolecular SS formation during freezing of Thiogel. Their mode of action is apparently osmotic. Glycerol and especially sucrose (but not dimethyl sulfoxide) even retard the very slow intermolecular SS formation in the absence of freezing. This may be due to the hydrated molecules acting as physical barriers.