A linear 11-compartment model was developed to describe and simulate the postprandial distribution of dietary nitrogen. The values of its 15 constant diffusion coefficients were estimated from the experimental measurement of (15)N nitrogen kinetics in the intestine, blood, and urine after the oral administration of (15)N-labeled milk protein in humans. Model structure development, parameter est...

of carbon and nitrogen in forest trees and affect growth responses to elevated carbon dioxide concentration ([CO2]). We investigated these effects in oak saplings (Quercus robur L.) exposed for two years to ambient or twice ambient [CO2] in combination with low(LN, 0.6 mmol N l) or high-nitrogen (HN, 6.1 mmol N l) fertilization. Autumn N retranslocation efficiency from senescing leaves was less...

Rumen microorganisms rapidly metabolized glycine at rates varying from 0.014 to 0.241 mumole of glycine per ml per min. The main metabolic products were carbon dioxide, acetic acid, and ammonia; little glycine was incorporated into bacterial protein. Use of carboxyl or methylene-labeled glycine showed that the carbon dioxide came mainly from the carboxyl of glycine, whereas both carbons of acet...

The ammonium ion is an indispensable nitrogen source for crops, especially paddy rice (Oryza sativa L. cv Nipponbare). Until now, it has been impossible to measure ammonium uptake and nitrogen movement in plants in real time. Using the new technologies of PETIS (positron emitting tracer imaging system) and PMPS (positron multi-probe system), we were able to visualize the real time translocation...

An Escherichia coli strain engineered for expression of the ribABGH genes of Bacillus subtilis was shown to produce 100 mg of the riboflavin precursor 6,7-dimethyl-8-ribityllumazine per liter of minimal medium. Growth of the recombinant strain in medium supplemented with [U-13C6]glucose and/or 15NH4Cl as single sources of carbon and/or nitrogen afforded 6,7-dimethyl-8-ribityllumazine universall...

15N-labeled fertilizer was applied to Sorghum at different rates (0, 100 kg N.ha -1 ) to 1m2 microplots and with two kind of water (well water “WW” and treated wastewater “TWW”) to Sorghum grown in field during 1997 and 1999. Increases in DM production, N uptake and 15 NRF were observed with TWW. About 17% and 36% of the 15Nfertilizer were recovered in the crop with TWW in 1997 and 1999, respec...

The two cyanide ligands in the assembled cluster of [FeFe] hydrogenase originate from exogenous l-tyrosine. Using selectively labeled tyrosine substrates, the cyanides were isotopically labeled via a recently developed in vitro maturation procedure allowing advanced electron paramagnetic resonance techniques to probe the electronic structure of the catalytic core of the enzyme. The ratio of the...

A method is presented for the calculation of REDOR dephasing for specifically labeled membrane-spanning peptides in uniformly aligned lipid bilayers under magic angle oriented sample spinning (MAOSS) conditions. Numerical simulations are performed for dephasing of (13)C signal by (15)N when the labels are placed in an alpha-helical peptide at the carbonyl of residue (i) and amide nitrogen of re...

In a previous paper (l), we reported on the incorporation of the methylene carbon of glycine in carotene in Phycomyces blakesleeanus and presented data suggesting that 8-aminolevulinic acid (ALA) had an effect similar to leucine in stimulating carotene production. We now present supplementary evidence on the correctness of the data dealing with labeled glycine by completing a carbon balance wit...

Loline alkaloids are saturated pyrrolizidines with a substituted 1-amino group and an oxygen bridge between C2 and C7, and are insecticidal metabolites of plant-symbiotic fungi (endophytes). Cultures of the endophyte, Neotyphodium uncinatum, incorporated labeled L-proline and L-homoserine into the 1-aminopyrrolizidine, N-formylloline. The A-ring carbons C1-C3 and the N1 were derived from L-homo...