The primed, continuous intravenous infusion of amino acids labeled with 13C together with measurement of isotopic enrichment in plasma is commonly used to study amino acid metabolism. However, a less invasive, oral infusion that also produces an isotopic steady state in CO2 and urine would be useful, particularly for pediatric studies. We measured the 13C enrichments of expired CO2, plasma and urine free phenylalanine and lysine and estimated flux and oxidation rates in adult humans (n = 12) who received a 4-h oral, primed, equal dose infusion of either L-[1-13C]phenylalanine, L-[1-13C]lysine (D-lysine = 1.6%) or L-[1-13C]lysine (D-lysine = 0.2%). Steady fed state conditions were established by feeding subjects eight hourly meals beginning 4 h before the start of the oral infusion protocol. Isotopic plateau in CO2, plasma and urine was achieved within 120 min of phenylalanine or lysine infusion. At isotopic plateau, the mean ratio of plasma to urine enrichment was 1.0 +/- 0.04 (SEM), 0. 39 +/- 0.03 and 0.97 +/- 0.02 for L-[1-13C]phenylalanine, L-[1-13C]lysine (D-lysine = 1.6%) and L-[1-13C]lysine (D-lysine= 0. 2%), respectively. There was good agreement between isotopic enrichment in plasma and urine for L-[1-13C]phenylalanine and L-[1-13C]lysine (D-lysine = 0.2%). However, use of L-[1-13C]lysine (D-lysine = 1.6%) resulted in significantly higher enrichment in urine, probably due to renal tubular discrimination of D-lysine. Mean flux rates for phenylalanine and lysine were consistent with the literature. Thus, the oral, primed, equal dose infusion produces the isotopic steady-state condition required for amino acid flux and oxidation determination within an 8-h period.
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http://dx.doi.org/10.1093/jn/128.11.1913 | DOI Listing |
Int J Mol Sci
January 2025
Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.
Sequences and three-dimensional structures of the four vertebrate arrestins are very similar, yet in sharp contrast to other subtypes, arrestin-1 demonstrates exquisite selectivity for the active phosphorylated form of its cognate receptor, rhodopsin. The N-terminus participates in receptor binding and serves as the anchor of the C-terminus, the release of which facilitates arrestin transition into a receptor-binding state. We tested the effects of substitutions of fourteen residues in the N-terminus of arrestin-1 on the binding to phosphorylated and unphosphorylated light-activated rhodopsin of wild-type protein and its enhanced mutant with C-terminal deletion that demonstrates higher binding to both functional forms of rhodopsin.
View Article and Find Full Text PDFPLoS One
January 2025
Escuela de Química, Universidad Industrial de Santander, Bucaramanga, Colombia.
Microorganisms tend to accumulate on surfaces, forming aggregates such as biofilms, which grant them resistance to various environmental stressors and antimicrobial agents. This ability has hindered the effective treatment of diseases caused by pathogenic microorganisms, including Salmonella, which is responsible for a significant number of deaths worldwide. This study aimed to compare the metabolic profiles of planktonic and sessile cells of Salmonella Enteritidis using a metabolomics approach.
View Article and Find Full Text PDFInt J Gen Med
January 2025
Post Graduate School of Jinzhou Medical University, Jinzhou, Liaoning, People's Republic of China.
Purpose: Acute coronary syndrome (ACS), comprising unstable angina and acute myocardial infarction, is the most dangerous and fatal form of coronary heart disease. This study evaluates serum bile acids (BAs) and amino acids (AAs) as potential predictors of AMI in UA patients.
Patients And Methods: A total of 72 Non-Coronary Artery Disease (NCAD) patients, 157 UA patients, and 79 AMI patients were analyzed.
J Pharm Biomed Anal
January 2025
Institute of Drug Metabolism and Pharmaceutical Analysis, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; Jinhua Institute of Zhejiang University, Jinhua 321036, China; State Key Laboratory of Advanced Drug Delivery and Release Systems, Zhejiang University, Hangzhou 310058, China. Electronic address:
A simple and fast LC-MS/MS method was developed and validated for simultaneous quantification of 20 L-amino acids (AAs) in human plasma. Chromatographic separation was achieved on an Agilent AdvanceBio Hilic column within 15 min via gradient elution with an aqueous solution containing 5 mM ammonium formate, 5 mM ammonium acetate and 0.1 % formic acid and an organic mobile phase containing 0.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
The use of proteins as intracellular probes and therapeutic tools is often limited by poor intracellular delivery. One approach to enabling intracellular protein delivery is to transform proteins into spherical nucleic acid (proSNA) nanoconstructs, with surfaces chemically modified with a dense shell of radially oriented DNA that can engage with cell-surface receptors that facilitate endocytosis. However, proteins often have a limited number of available reactive surface residues for DNA conjugation such that the extent of DNA loading and cellular uptake is restricted.
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