Dimethylsulfoxide influence

Finally, we can estimate the comparative influence of plasma and serum proteins with molecular weights > 20,000 on the cell-serum and cell-plasma interfaces, as opposed to surface-active solutes such as ethylene glycol or dimethylsulfoxide (6). The latter will adsorb at the interfaces to an extent that is comparable with their adsorption at the liquid-... 

Permeability. As a diflFusion barrier, SC is most eflFective when dry, less eflFective when hydrated, and still less eflFective when treated with solvents such as dimethylsulfoxide (DMSO) (16, 92). The hydrating eflFect of increased relative humidity, occlusion, or immersion can be visualized as separation of hygroscopic and protein elements to create diflFusion channels containing free water (20, 69, 71). Obviously, water and its solutes should be more mobile in free-water channels than in bound water. The degree of hydration also can be influenced indirectly by organic solvents that hold water (glycol, DMSO) (18) or that modify surfaces (surfactants) (16, 18). 

Remaining parts of solvents (e.g., dimethylsulfoxide (DMSO), ethanol, dichlormethane, and acetone) influence, even in small quantities, the nucleation of ice crystals and its growth. Normally they will also reduce 7, [5-7]. The solvents will also change the pressure reading on a thermoelectric (TM) instrument and... 

Asker, A.F. Canady, D. Influence of certain additives on the photostabilizing effect of dimethylsulfoxide for sodium nitroprusside solutions. Drug Dev. Ind. Pharm. 1984, 10, 1025-1039. 

Chemical modification of polymer-bound active ester groups is also subject to strong solvent effects. In copolyfAOTcp-styrere), both aminolysis and transesterification with primary alcohols are positively influenced by solvents in the order of dimethylformamide (DMF) > dioxan > diloroform > chlorobenzene > dimethylsulfoxide (DMSO). However, trans-esterification with phenols proceeds in dioxan, but not in DMF. The last-nan d solvent effect is probably related to inactivation of the phenolate ion in DMF, as observed ako for the acylation of polymer-bound phenolic groups by soluble trichlorophenyl esters [64]. 

In general one has to realize that each deprotection reaction is specifically influenced by the chain length of the polymer-bound peptide and by the acutal N-terminal amino acid residue, because of the differences in solvation of the individual amino acids and of the whole peptide in relation to the properties of the support. For this reason, for example, 5.35 N HCl in dimethylsulfoxide/dichloromethane (1 1) was employed [ 115] to deal with the problem of different solvations. In another example, mercaptoethane sulfonic acid [116] was utilized in diluted solution to deprotect N-terminal Boc-tryptophane without harming the indole moiety. 

In the first series of experiments, 0.1 ml of the neat solvents were applied with a pipette to the forearm skin of healthy subjects and were allowed to spread freely. As can be seen from Table 3, only one solvent (dimethylsulfoxide) caused an increase in skin blood flow. The sites looked normal to the naked eye. In the second series of experiments, the neat solvents were applied in excess (1.5 ml/3.1 cm ) using a glass ring as a reservoir and attached with rubber bands to the forearm. Three different exposure times were used (1, 5, and 15 min) and, as can be seen from Table 3, the solvents varied greatly in their effects on skin blood flow. The most potent solvents were dimethylsulfoxide and trichloroethylene, while 15 min of exposure in excess to methyl ethyl ketone, propylene glycol, ethanol and water did not influence skin blood flow. 

Oedema caused by repeated skin exposure to solvents can be quantified with a rather unsophisticated device the caliper (Wahiberg 1984a). Results of measurements of skin-fold thickness of experimental animals treated once daily with neat solvents are summarised in Table 4. Trichloroethylene and dimethylsulfoxide seem to be potent oedema-inducing solvents as well as influencing skin blood flow in man (Table 3). 

The first step is crucial to attain high molecular weight, and the second has a great influence in the final nature of the polyimide since a quantitative conversion in the cyclodehydration process is needed to have a pure, fully cyclized polyimide. Highly polar solvents are suitable media to dissolve monomers and poly(amic acid)s. A, A -dimethyl-acetamide (DMA), A,A-dimethylformamide (DMF), dimethylsulfoxide (DMSO), and A-methyl-2-pyrrolidinone (NMP) are the most adequate. Purity of solvents and reactants, and strict stoichiometric balance are requirements of polycondensation reactions that fully fit polyimides synthesis, where a careful control of the reaction variables is essential to achieve high molecular weight [17-19]. For instance, rigorous exclusion of water is a key condition, as well as a moderate polymerization temperature (about 0 °C or less) in poly(amic acid) formation in order to limit the competition of side reactions and a premature release of imidation water. 

Alak and Armstrong (107,108,112,113) investigated the influence of different silicas and binders on the separation behavior of P-cyclodextrin TLC plates. Besides nine racemates, three diastereomeric compounds and six structural isomers were separated. Wilson (109) impregnated silica plates with a 1% solution of P-CD in ethanol-dimethylsulfoxide (80 20 by volume) racemic mandelic acid was barely separated, and the antipode separation of P-blockers was not possible. Armstrong et al. (110) were the first to describe application of P-cyclodextrin as a chiral eluent additive for separations on reversed-phase TLC plates. The success of separation was strongly dependent on type and quantity of modifier applied, but above all on the concentration of P-CD. The low solubility of 3-CD in water (0.017 M, 2S C) can be improved by addition of urea sodium chloride stabilizes the binder of the RP plates. Compared to 3-CD bonded phases, a reversed retention behavior was noticed, the D-enantiomer eluting above the L-isomer. The separation of steroid epimers and other diastereomeric classes of compounds is also possible with this technique. Hydroxypropyl and hydroxyethyl P-... 

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