Protein denaturation alcohol effects

Polar solvents have a log P < 2, moderate solvents have a log P in the range 2apolar solvents log P > 4 (Table 1). Synthesis is best achieved in solvents of intermediate polarity that are able to partially solubilize both the sugar and enzyme, or in solvents with a log P value greater than 1.5 that do not affect the hydration shell of the enzyme and so denature the protein. Tertiary alcohols are particularly effective solvents in this respect as they cannot react with lipases due to steric hindrance at the hydroxy group and their boiling points facilitate their removal after reaction. tert-Butyl alcohol catalyzed by lipase has been employed for sugar acylations [40-42]. Other solvents that have been utilized include 2-pyrrolidone [43] for the synthesis of sorbitol ester derivatives. Pyridine and biphasic mixtures of solvents such as benzene/pyridine and tert-hvXy alcohol/hexane have also been used. 

Sugar alcohols have also found appHcation in foods containing sugars. Sorbitol is an effective cryoprotectant in surimi, preventing denaturation of the muscle protein during fro2en storage. 

Astringents are designed to dry the skin, denature skin proteins, and tighten or reduce the size of pore openings on the skin surface. These products can have antimicrobial effects and are frequendy buffered to lower the pH of skin. They are perfumed, hydro-alcohoHc solutions of weak acids, such as tannic acid or potassium alum, and various plant extracts, such as bitch leaf extract. The alcohol is not only a suitable solvent but also helps remove excess sebum and soil from the skin. After-shave lotions generally function as astringents. 

Similarly to the above-mentioned entrapment of proteins by biomimetic routes, the sol-gel procedure is a useful method for the encapsulation of enzymes and other biological material due to the mild conditions required for the preparation of the silica networks [54,55]. The confinement of the enzyme in the pores of the silica matrix preserves its catalytic activity, since it prevents irreversible structural deformations in the biomolecule. The silica matrix may exert a protective effect against enzyme denaturation even under harsh conditions, as recently reported by Frenkel-Mullerad and Avnir [56] for physically trapped phosphatase enzymes within silica matrices (Figure 1.3). A wide number of organoalkoxy- and alkoxy-silanes have been employed for this purpose, as extensively reviewed by Gill and Ballesteros [57], and the resulting materials have been applied in the construction of optical and electrochemical biosensor devices. Optimization of the sol-gel process is required to prevent denaturation of encapsulated enzymes. Alcohol released during the... 

In the past, dissociation of the nucleoprotein complex has been brought about by salt solutions or by heat denaturation,129 but, more recently, decomposition has been effected by hydrolysis with trypsin,126 or by the use of dodecyl sodium sulfate130 or strontium nitrate.131 Some virus nucleoproteins are decomposed by ethyl alcohol.132 This effect may be similar to that of alcohol on the ribonucleoproteins of mammalian tissues. If minced liver is denatured with alcohol, and the dried tissue powder is extracted with 10% sodium chloride, the ribonucleoproteins are decomposed to give a soluble sodium ribonucleate while the deoxyribonucleoproteins are unaffected.133 On the other hand, extraction with 10 % sodium chloride is not satisfactory unless the proteins have first been denatured with alcohol. Denaturation also serves to inactivate enzymes of the tissues which might otherwise bring about degradation of the nucleic acid during extraction. 

The above observations provide a clear demonstration that cosolvents in selected ranges of concentration create reversible perturbations of protein similar to those induced by other modifiers. The reversibility of the cosolvent effect is a prerequisite to cosolvent use and will depend on the concentration of cosolvent, which in turn will vary markedly with the type of solvent used. For instance, polyols can be used at concentrations up to 8 Af while methanol at 3 M causes the appearance of a new absorption band (410 nm) and, after further increases in concentration, an irreversible conversion of cytochrome P-450 into P-420. Other aliphatic alcohols cause denaturation at much lower concentrations. 

Formulation additives used in topical drug or pesticide formulations can alter the stratum comeum barrier. Surfactants are least likely to be absorbed, but they can alter the lipid pathway by fluidization and delipidization of lipids, and proteins within the keratinocytes can become denatured. This is mostly likely associated with formulations containing anionic surfactants than non-ionic surfactants. Similar effects can be observed with solvents. Solvents can partition into the intercellular lipids, thereby changing membrane lipophilicity and barrier properties in the following order ether/acetone > DMSO > ethanol > water. Higher alcohols and oils do not damage the skin, but they can act as a depot for lipophilic drugs on the skin surface. The presence of water in several of these formulations can hydrate the skin. Skin occlusion with fabric or transdermal patches, creams, and ointments can increase epidermal hydration, which can increase permeability. 

One of the critical factors in excipient selection and concentration is the effect on preferential hydration of the biopharmaceutical product [53, 54], Preferential hydration refers to the hydration layers on the outer surface of the protein and can be utilized to thermodynamically explain both stability enhancement and denatur-ation. Typical excipients used in protein formulations include albumin, amino acids, carbohydrates, chelating and reducing agents, cyclodextrins, polyhydric alcohols, polyethylene glycol, salts, and surfactants. Several of these excipients increase the preferential hydration of the protein and thus enhance its stability. Cosolvents need to be added in a concentration that will ensure their exclusion from the protein surface and enhance stability [54], A more comprehensive review of excipients utilized for biopharmaceutical drug products is available elsewhere [48],... 

Ethyl alcohol is used in antifreeze products, and also as a fuel a solution of 70-85% of ethyl alcohol is commonly used as a disinfectant. It kills organisms by denaturing their proteins and dissolving their liquids and it is effective against most bacteria, fungi and many viruses though ineffective against bacterial spores. 

Trifluoroethanol has been used to denature proteins and to stabilize structures in peptides via protonation. Direct interactions of the trifluoroethanol with the peptide chain have been inferred from changes in NMR chemical shift and line width. Site-specific interaction has not yet been demonstrated experimentally in solution [39, 40]. Neutron diffraction studies on a similar protonation of lysozyme by ethanol indicate that trifluoroethanol is likely to bind to the carbonyl oxygen on the main chain of the peptide. It is inferred that such a site-specific interacting nature of trifluoroethanol resulted in the enhancement of intramolecular hydrogen bonding of the amide group in the peptide to minimize its exposure to the alcohol. A structural transition from (3 -sheet to a -helix of the Taiwan cobra poison peptide, which is induced by an interaction of trifluoroethanol, has been reported [41 ]. Details on the effects of trifluoroethanol on peptides and proteins are summarized in Ref. [42]. 

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