[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: Hb O-Tibesti, carries in the same chain the substitution of Hb O-Arab [β121(GH4)Glu → Lys] and that of Hb Hamilton [β11(A8)Val → Ile]. Hb O-Tibesti may be distinguished from Hb O-Arab by polyacrylamide gel electrophoresis in the presence of urea and Triton-X100, and by reversed phase high performance liquid chromatography. It was found in a compound heterozygous condition with Hb S [β6(A3)Glu → Val] in a child of Chad-Sudanese descent, suffering from a sickle cell syndrome. Compared to the classical description of the Hb S/Hb O-Arab association, the additional Hb Hamilton mutation does not seem to modify the clinical presentation.
[Show abstract][Hide abstract] ABSTRACT: Hb Melusine [α114(GH2)Pro→Ser] was found in an Algerian patient during a systematic screening for hemoglobinopathies performed in Luxembourg. The abnormal hemoglobin was suspected when a thickening of the Hb A band was observed by isoelectrofocusing. The mutant hemoglobin was silent in all other electrophoretic methods used for presumptive diagnosis with the exception of globin electrophoresis in the presence of Triton X-100. This technique revealed an α chain considerably more hydrophobic than normal. The structural abnormality of Hb Melusine concerns position α114(GH2) that belongs to a cluster of hydrophobic residues localized in the N-terminal half of the αT-12b tryptic peptide. It has been shown in the case of another variant of that position (Hb Nouakchott), that the replacement of the Pro GH2 by a Leu was responsible for a dramatic increase in the retention time of the a polypeptide chain during reversed phase high performance liquid chromatography, much higher than that reported for similar substitutions in other regions of the hemoglobin molecule.
[Show abstract][Hide abstract] ABSTRACT: Hb Sitia [β128(H6)Ala → Val] was found in a Greek female with slightly reduced red blood cell indices. The abnormal hemoglobin was indistinguishable from Hb A by electrophoresis but eluted after Hb A on cation exchange high performance liquid chromatography. DNA sequence analysis revealed a GCT → GTT mutation at codon 128, which is predicted to encode an Ala → Val substitution. This was confirmed by mass spectrometry analyses of the β-globin chain. Since alanine at β128(H6) interacts with several amino acids of the α1β1 contact, its replacement by a larger residue results in a mild instability of the molecule and slight modifications of the oxygen binding properties.
[Show abstract][Hide abstract] ABSTRACT: Two new fetal hemoglobin variants affecting the Gγ chain are reported. Hb F-Clamart was found during investigation of a French newborn who presented with a mild microcytemia. the second variant was found during neonatal screening for hemoglobinopathies of 30,000 babies from a population-at-risk living in the Paris region. It was named Hb F-Ouled Rabah because its structural modification and ethnic distribution is similar to that of Hb D-Ouled Rabah [Gγ19(B1)AsnLys]. Hb F-Ouled Rabah is clinically silent and occurs at a frequency of ca. 0.1% in newborns originating from Maghreb. Structural characterization of both variants was done by protein chemistry methods, including amino acids analysis and mass spectrometry.
[Show abstract][Hide abstract] ABSTRACT: Hb Uxbridge [β20(B2)Val → GIy] was found in an English family during a neonatal hemoglobinopathy screening program. In both the child and the parent carrying this hemoglobin variant, the red cell parameters were normal. By isoelectrofocusing Hb Uxbridge appeared to have an isoelectric point slightly higher than Hb A but was silent on cellulose acetate and acid gel electrophoresis. Structural modifications affecting position β20(B2) have been demonstrated to be responsible for a high oxygen affinity and polycythemia in Hb Olympia (Val → Met) and Hb Trölhattan (Val → GIu). In the case of Hb Uxbridge, despite an alteration of the same site, the oxygen binding parameters of the patient's hemolysate showed only a mild (ca. 20%) increase in oxygen affinity.
[Show abstract][Hide abstract] ABSTRACT: Analysis of globin chains by reversed phase high performance liquid chromatography, used as an additional tool for characterizing hemoglobin variants, has led to the discovery of a new class of variants that display only differences in hydrophobicity. Two such variants are here described. Hb Ernz was found in a man of Italian origin who was polycythemic, and in two of his three daughters who were hematologically normal. Hb Renert, a slightly unstable variant, was found in a man from Cape Verde who also carried Hb S and presented with chronic hemolysis. The structural abnormalities were characterized by protein structure methods involving reversed phase high performance liquid chromatographic separations of globins and peptides, followed by mass spectrometry studies (electrospray, ion trap, tandem mass spectrom-etry).
[Show abstract][Hide abstract] ABSTRACT: Hb Bushey, found in a Chinese baby and his father, is a new variant with a point mutation leading to the substitution Phe→tLeu at position β122. Hb Casablanca, found in a family from Morocco, is a further example of a hemoglobin variant that carries two abnormalities in the same chain; the first is identical to that of Hb Bushey and the second to that of Hb J-Antakya [β65 (E9)Lys→Met]. Structural abnormalities of both Hbs were determined by protein chemistry methods including electrospray and tandem mass spectrometry. Their stability and oxygen binding properties were found to be identical to those of Hb A. Various mechanisms that may lead to two point mutations in the same chain are reviewed briefly.
[Show abstract][Hide abstract] ABSTRACT: ABSTRACTA chemically defined medium with glutamic acid as nitrogen source was devised for the culture of two species of Monascus (M. ruber and M. purpureus), resulting in optimum production of their pigments and their chemical structures (both free and complexed) were compared. Structural data on two major complex pigments in aqueous solution were obtained by IR, UV, NMR and MS. They were free pigments linked to glutamic acid by amino groups, where nitrogen replaced the pyronoid oxygen.
[Show abstract][Hide abstract] ABSTRACT: The oxyanion [MH]− from several methylglycosides were generated by fast atom bombardment and their decomposition was studied by mass-analysed ion kinetic energy spectrometry. The main decomposition pathway is the loss of methanol. The hydroxylic hydrogen arises by proton transfer from the hydroxyl groups of the sugar. In the gluco-series, no anomeric effect is found. The absence of either the hydroxyl groups at C-2 or C-6 does not inhibit the glycosidic cleavage. However, the blocking of both the hydroxyl groups at C-4 and C-6, by a benzylidene group or two methyl groups, inhibit completely the glycosidic cleavage. From these results, it is proposed that the glycosidic cleavage occurs after opening the sugar ring by a vicinal attack of an oxyanion at C-6 or C-4 to the C-5 carbon atom. Then, the ionized hemi-acetals fragment into a methanolate anion and a 5,6- or 4,5-anhydrosugar which exchange another proton before their separation into charged and neutral species.
[Show abstract][Hide abstract] ABSTRACT: The distinction between 17-epimeric 3,17-dioxygenated hydroxyandrostanes has been made by comparison of both their methane or ammonia positive and OH− negative chemical ionization (CI) mass spectra. In the methane or ammonia positive CI, the 17α-configuration in the eight stereoisomeric 5ξ-androstane-3ξ,17ξ-diols can be determined by the relative abundances of the ion [MH2 H2O]+. In the ammonia CI spectra, the ion [M+NH4H2O]+ possesses only a low abundance, but a comparison of the relative rates of the loss of water v. the loss of ammonia from [M.NH4]+ in the second field-free region allows a clear distinction to be made between the 17α- and 17β-series. In the OH− negative CI mass spectra, the 5ξ-androstane-3-one-17ξ-ols produce an intense ion [MHH2O]− in the 17α-series only.