With the objective of establishing the importance of water flexibility in empirical models which explicitly include nuclear quantum effects, we have carried out path integral Monte Carlo simulations in water clusters with up to seven molecules. Two recently developed models have been used for comparison: the rigid TIP4PQ/2005 and the flexible q-TIP4P/F models, both inspired by the rigid TIP4P/2...

Tritiated water and tritiated substrates have been used to study exchange reactions catalyzed by Escherichia coli 2-oxo-4-hydroxyglutarate aldolase (4-hydroxy-2-oxoglutarate glyoxylate-lyase, EC 4.1.3.16, 2-oxo-4-hydroxyglutarate in equilibrium pyruvate + glyoxylate). With pyruvate, the enzyme catalyzes a rapid first-order exchange of all three methyl hydrogens in the absence of added acceptor ...

The absorption of undiluted phthalate diesters [dimethyl phthalate (DMP), diethylphthalate (DEP), dibutyl phthalate (DBP) and di-(2-ethylhexyl)phthalate (DEHP)] has been measured in vitro through human and rat epidermal membranes. Epidermal membranes were set up in glass diffusion cells and their permeability to tritiated water measured to establish the integrity of the skin before the phthalat...

Solutions of (14)C-sugars in tritiated water or solutions of (14)C- and (3)H-sugars were perfused by gravity through the xylem vessels of excised tomato internodes (Lycopersicon esculentum) mostly during 2 hours.Mass flow of a solution in plant vessels is found not to be in conflict with different mass transfer rates of sugar and water molecules. It is explained by individual lateral escape rat...

IN attempts to label the nuclei of intact amphibian embryos with tritiated thymidine we found, in agreement with other authors (Tencer, 1961; Quertier, 1962; Chibon, 1962), that when the nucleoside is dissolved in tap water or media of low salt concentration it fails to enter the embryo. However, when tritiated thymidine was either injected into the embryo or applied to isolated tissues immerse...