Detail of "87-32-1"

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Thermal stability of human albumin measured by differential scanning calorimetry

Thermal stability of human albumin measured by differential scanning calorimetry. II. Effects of isomers of N-acetyltryptophanate and tryptophanate, pH, reheating, and dimerization. Ross, P. D.; Finlayson, J. S.; Shrake, A. (Off. Biol., Natl. Inst. Arthritis, Diabetes, Dig. Kidney Dis., Bethesda, MD, USA). Vox Sang., 47(1), 19-27 (English) 1984. CODEN: VOSAAD. ISSN: 0042-9007. DOCUMENT TYPE: Journal CA Section: 63 (Pharmaceuticals) The thermal stability of undefatted human albumin prepns. at 5% concn. and neutral pH in 145 mM Na+ was investigated by DSC . At 30 and 4 mM N-acetyltryptophan [87-32-1], the thermogram for previously unheated albumin monomer is independent of the stereochem. of this ligand; thus, the affinity of the protein must be the same for the L- [1218-34-4] and D- [2280-01-5] isomers in the temp. range of thermal denaturation (62-86°). L-Tryptophan [73-22-3] (26 mM) bestows a slight increase in stability on previously unheated monomer, whereas 27 mM D-tryptophan [153-94-6] has no effect, a result consistent with the reported weaker binding of the D-isomer. Previously unheated albumin monomer shows slightly greater thermal stability at pH 6.4 than at pH 7.4. The tracing of differential heat capacity vs. temp. (thermogram) for monomer from once heated albumin, i.e. once processed and once heated normal serum albumin (NSA), is almost identical to that for previously unheated monomer. Monomer prepd. from outdated, multiply reprocessed, multiply reheated NSA (old monomer) has the same corresponding denaturation temps. as previously unheated monomer; the corresponding dimer (old dimer) is slightly less stable. Thermograms for old monomer and old dimer, like those for previously unheated monomer, comprise 2 denaturation peaks (endotherms). Their endotherms, however, are very broad, reflecting the great heterogeneity of the old proteins. The thermogram for old monomer remains broad even in the presence of N-acetyltryptophan and/or Na caprylate [1984-06-1]. Older dimer does not dissoc. when undergoing thermal denaturation.

Thermal stability of human albumin measured by differential scanning calorimetry

Thermal stability of human albumin measured by differential scanning calorimetry. I. Effects of caprylate and N-acetyltryptophanate. Shrake, A.; Finlayson, J. S.; Ross, P. D. (Off. Biol., Natl. Inst. Arthritis, Diabetes, Dig. Kidney Dis., Bethesda, MD, USA). Vox Sang., 47(1), 7-18 (English) 1984. CODEN: VOSAAD. ISSN: 0042-9007. DOCUMENT TYPE: Journal CA Section: 63 (Pharmaceuticals) The thermal stability of 5% previously unheated, undefatted human albumin monomer in 145 mM Na+, pH 7.0 was investigated by differential scanning calorimetry (DSC) as a function of added Na caprylate [1984-06-1] and/or N-acetyl-DL-tryptophan [87-32-1]. Caprylate was substantially more effective than N-acetyl-DL-tryptophan in protecting the protein against thermal denaturation at a given level or at a satg. level of stabilizer. The tracing of the differential heat capacity vs. temp. (thermogram) for this undefatted monomer that contained 1.5 mol endogenous, long-chain fatty acid (LCFA)/mol monomer exhibits 2 denaturation peaks (endotherms) in the absence of stabilizer. The endotherm with the lower denaturation temp. (Td) comprises 70% of the total heat of denaturation and also corresponds to irreversible denaturation and pptn. of 70% of the albumin. This endotherm is assocd. with more thermally labile protein species contg. low levels of LCFA. The endotherm with the higher Td is assocd. with more stable protein species contg. high levels of LCFA. Thus, the 2 endotherms are not related to the proposed domain structure of the protein but result from an uneven LCFA distribution that is due to preexisting heterogeneity in the albumin and/or heterogeneity that arises during the DSC expt. Binding data do not support a preexisting uneven distribution of sufficient magnitude to explain the exptl. results. A complementary explanation is that an uneven fatty acid distribution arises during the DSC expt. by migration of LCFA from the more labile species to the more stable as the former unfold; such migration would cause further stabilization of the latter.