Lanthanide DOTA-tetraglycinate (LnDOTA-(gly)₄⁻) complexes contain four magnetically equivalent amide protons that exchange with protons of bulk water. The rate of this base catalyzed exchange process has been measured using chemical exchange saturation transfer (CEST) NMR techniques as a function of solution pH for various paramagnetic LnDOTA-(gly)₄⁻ complexes to evaluate the effects of lanthan...

The K1 capsule is an essential virulence determinant of Escherichia coli strains that cause meningitis in neonates. Biosynthesis and transport of the capsule, an alpha-2,8-linked polymer of sialic acid, are encoded by the 17-kb kps gene cluster. We deleted neuC, a K1 gene implicated in sialic acid synthesis, from the chromosome of EV36, a K-12-K1 hybrid, by allelic exchange. Exogenously added s...

A novel Na/H exchange activity that requires Cl was recently identified in the apical membrane of crypt cells of the rat distal colon. This study explores the nature of the coupling of Cl and Na/H exchange. A concentration of 100 μM 5-nitro-2-(3-phenylpropylamino)benzoic acid, a Cl channel blocker, inhibited the Cl dependence of both proton gradient-driven22Na uptake from crypt cell apical memb...

Proton exchange membrane fuel cells (PEMFCs) are electrochemical devices that show the highest power densities compared to the other type of fuel cell. In this work, nanocomposite membranes used for proton exchange membrane fuel cells as poly(vinyl alcohol)/La2Ce2O7 (PVA-LC) with the aim of increasing the water uptake and proton conductivity. Glutaraldehyde (GA) was used as cross linking agent ...

Sulfonated poly (ether ether ketone) (SPEEK) with a low degree of sulfonation (DS = 40%) was prepared for proton exchange membrane fuel cells (PEMFC). Poly (ether ether ketone) (PEEK) was sulfonated in concentrated H2SO4 under N2 atmosphere and characterized by the hydrogen nuclear magnetic resonance (H-NMR) technique. After preparation of the SPEEK polymer, the obtained polymer was dissolved i...

Orotidine 5'-monophosphate decarboxylase (OMPDC) catalyzes the exchange for deuterium from solvent D(2)O of the C-6 proton of 1-(β-d-erythrofuranosyl)-5-fluorouracil (FEU), a phosphodianion truncated product analog. The deuterium exchange reaction of FEU is accelerated 1.8 × 10(4)-fold by 1 M phosphite dianion (HPO(3)(2-)). This corresponds to a 5.8 kcal/mol stabilization of the vinyl carbanion...

Diaminopimelic acid epimerase was purified from Escherichia coli. The enzyme is a monomer of Mr = 34,000. Diaminopimelic acid epimerase is not a pyridoxal phosphate-dependent enzyme: there is no evidence for pyridoxal phosphate in the ultraviolet spectrum of the purified enzyme, and the epimerase is not inactivated by carbonyl reagents such as hydroxylamine and sodium borohydride. Exchange of t...

4,5-Dicyano-1H-[1,2,3]-Triazole (DCTz) exhibits a very low proton affinity. This makes it a possible water replacement for proton transport in high temperature polymer electrolyte membranes. A detailed investigation is carried out to define various physical properties as well as the proton transfer characteristics of DCTz. Thermogravimetric analysis showed that DCTz as well as DCTz salts are th...