: 1h nmr spectra of a series of enaminones r-co-ch=c(nhch2ph)-r  [1, r=ch3; 2, r=c6h5; 3, r=cf3; 4, r=ch2ch2ch2; 5, r=ch2c(ch3)2ch2], were obtained in the presence of trifluoroacetic acid in cdcl3 or dmso-d6 at 28 °c. steric, solvent, electronic and hydrogen bonding effects on the rates of acid-catalyzed nh proton exchanges were investigated. rate constants were calculated by 1h nmr line shape ...

A method for detecting structure in marginally stable forms of a protein is described. The principle is to measure amide proton exchange rates in the absence and presence of varying concentrations of a denaturant. Unfolding of structure by the denaturant is reflected by an acceleration of amide proton exchange rates, after correction for the effects of the denaturant on the intrinsic rate of ex...

: 1H NMR spectra of a series of enaminones R-CO-CH=C(NHCH2Ph)-R  [1, R=CH3; 2, R=C6H5; 3, R=CF3; 4, R=CH2CH2CH2; 5, R=CH2C(CH3)2CH2], were obtained in the presence of trifluoroacetic acid in CDCl3 or DMSO-d6 at 28 °C. S...

Nearest-neighbor inductive effects are known to influence amide proton exchange. Here we show that longrange electrostatic interactions also have a significant effect on the rate of amide proton exchange. We have measured the effects of salt (NaC1) on the exchange rates of the neutral polypeptide poly(DL-alanine) (PDLA) and of the positively charged polymer poly(DL-lysine) (PDLL). Our results s...

Regioselective labelling of arene rings via electrophilic exchange is often dictated by the electronic environment caused by substituents present on the aromatic system. Previously, we observed the presence of a t-butyl group, either covalently bond or added as an external reagent, could impart deuterium exchange to the unactivated, C1-position of estrone. Here, we provide nuclear magnetic reso...

In this study, proton conductive composite membranes were produced by using a poly(methylmethacrylate-co-maleic anhydride) (P(MMA-co-MAH)) copolymer and phosphotungstic Acid (PWA) as an additive of the proton conductive agent. P(MMA/MAH) 70/30, 50/50, and 30/70 were synthesized using a free radical polymerization reaction. PWA with a concentration of 2% was added to...

We compare the effect of buffers on the catalysis by bovine carbonic anhydrase, human carbonic anhydrase C (HCA 0, and human carbonic anhydrase B (HCA B) of two types of ‘“0 exchange. Type I, resulting from the hydrationdehydration reaction, is the exchange of IsO between CO, and water. Type II is the exchange of IsO between ‘*Ccontaining and ‘“C-containing species of COZ. Imidazole, 2,4-lutidi...

heterogeneous proton exchange membranes (pem) are synthesized using the dry phase inversion technique. the casting solutions are prepared by dispersing a finely ground cation exchange resin particle in n,n-dimethylacetamide (dmac) solution of polyvinyl-chloride (pvc). results show that ion exchange capacity is increased with the addition of 1 %-wt nanosilica (from 0.14 to 0.27 meq/g) while it i...

Heterogeneous proton exchange membranes (PEM) are synthesized using the dry phase inversion technique. The casting solutions are prepared by dispersing a finely ground cation exchange resin particle in N,N-dimethylacetamide (DMAc) solution of polyvinyl-chloride (PVC). Results show that ion exchange capacity is increased with the addition of 1 %-wt nanosilica (from 0.14 to 0.27 meq/g) while it i...