Surface-enhanced Raman spectroscopy of chernozem humic acid and their fractions obtained by coupled size exclusion chromatography-polyacrylamide gel electrophoresis (SEC-PAGE).

A humic acid extracted from a chernozem soil was fractionated combining size exclusion chromatography and polyacrylamide electrophoresis (SEC-PAGE). Three fractions named A, B, and C+D, with different electrophoretic mobilities and molecular sizes (MS), were obtained and subsequently characterized by thermochemolysis and surface-enhanced Raman spectroscopy (SERS). The data confirmed that fraction A, with the higher MS, was more aliphatic than fractions B and C+D and, in turn, fractions with lower MS (B and C+D) denoted an enrichment in lignin residues. These structural features explain conformational changes when varying the pH in the humic fraction A and indicated that combination of the two techniques is a good approach for characterizing humic substances.

Oligomycin sensitivity-conferring protein (OSCP) of beef heart mitochondria. Internal sequence homology and structural relationship with other proteins.

Structural analysis of oligomycin sensitivity-conferring protein (OSCP) revealed repeating sequences (residues 1-89, 105-190) suggesting an evolution of the protein by gene duplication. In addition to the reported homology with the delta-subunit of Escherichia coli F1ATPase, OSCP also shows a certain homology with the b-subunit of E. coli F0 and the ADP/ATP carrier of mitochondria.

Amino acid sequence of the oligomycin sensitivity-conferring protein (OSCP) of beef-heart mitochondria and its homology with the delta-subunit of the F1-ATPase of Escherichia coli.

The complete amino acid sequence of the oligomycin sensitivity-conferring protein (OSCP) of beef-heart mitochondria is reported. The protein contains 190 amino acids and has a molecular mass of 20 967. Its structure is characterized by a concentration of charged amino acids in the two terminal segments (N 1-77 and C 128-190) of the protein, whereas its central region is more hydrophobic. The earlier reported homology of the protein with the delta-subunit of E. coli F1, based on the terminal amino acid sequences of OSCP, is further substantiated.

Evaluation of the transformation of organic matter to humic substances in compost by coupling sec-page.

Humic acids (HAs) from soil and compost at the beginning (S0) and at the end of the stabilization process after 130 days (S130) have been fractionated by coupling size exclusion chromatography (SEC) and polyacrylamide gel electrophoresis (PAGE). Preparative quantities of HA fractions (HAFs) with different molecular sizes (MSs) and exactly defined electrophoretic mobility (EMs) have been obtained from all samples and the HAFs weight content has been studied. A high degree of similarity in HAFs weight content between soil HA and a stabilized compost HAs130 has been observed. Such data seem to be reliable for monitoring the evolution of the compost organic matter to humic substances for their agricultural uses.

Compositional differences between soil humic acids extracted by various methods as evidenced by photosensitizing and electrophoretic properties.

Humic acids (HAs) were isolated from Elliott soil provided by the International Humic Substances Society (1BS102M) by three commonly used methods: (i) 0.1M NaOH (EI-HA), (ii) neutral 0.1M Na(4)P(2)O(7) (L-HA) and subsequent 0.1M NaOH (S-HA), and (iii) 0.1M NaOH+0.1M Na(4)P(2)O(7) (NP-HA). The objective was to evaluate the impact of these extractants on the photosensitizing properties of the isolated HAs. HAs were analyzed for their elemental composition, functional acid groups content, absorption and emission properties, electrophoretic characteristics and ability to produce singlet oxygen using furfuryl alcohol (FFA) as a scavenger. L-HA was slightly more aromatic and oxygenated than the other HAs and contained a higher portion of long-wavelength fluorophores and macromolecules showing low molecular size (MS) and high electrophoretic mobility. L-HA also gave a rate of FFA photooxygenation between 1.25- and 1.6-fold higher than the other HAs. This suggests that the free humic macromolecules ionized at pH 7 and/or weakly bounded on mineral surfaces via cation bridges are of relatively low MS and contribute significantly to the photosensitizing and long-wavelength emitting properties. Differences among the other HAs were more subtle, but the parallel evolution of the reactivity and electrophoretic characteristics was observed. Photochemical and electrophoretic measurements seem to be sensitive indicators to evaluate differences among the extraction procedures of HAs.