title: Lactic acid and protein interactions: implications for the NMR visibility of lactate in biological systems.
abstract: The addition of bovine serum albumin (BSA) to a solution of lactate and alanine resulted in the disappearance of the 1H-NMR resonances from lactate but not alanine. As temperature is increased lactate becomes increasingly NMR visible and after heating above 65 degreesC and cooling to 25 degreesC lactate binding is reduced. With a concentration of 0.2 mM BSA, there was a linear relationship between NMR visible lactate versus total lactate over a range of lactate concentrations of 0.2-35 mM (slope 0.384+/-0.003) indicating that approx. 60% of the added lactate is not visible in the 1H-NMR spectrum. With a 0.1 mM BSA solution, however, the slope was markedly higher indicating that under these conditions only 25-30% of the lactate was NMR invisible. The results from this study indicate that decreased NMR visibility of lactate in proteinaceous solutions is due to non-specific binding which is dependent on the tertiary structure of the protein. This has important implications not only for the interpretation of in vivo 1H-NMR experiments but also for 13C, and 14C studies of metabolism.
authors.affiliation: Division of NMR Research, Department of Radiology, 217 Traylor Building, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205-2195, USA. jchatham@mri.jhu.edu
authors.forename: J C
authors.initials: JC
authors.lastname: Chatham
authors.forename: J R
authors.initials: JR
authors.lastname: Forder
mesh_terms: D007773:Lactates / Q000032:analysis* / Q000378:metabolism; D019344:Lactic Acid / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine; D013696:Temperature
chemical_list: D007773:Lactates; D011506:Proteins; D012710:Serum Albumin, Bovine; D019344:Lactic Acid