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Presents an investigation of the sequencing of 65 amino acid residues at the carboxyl-terminus. Use of methods such as enzymic or chemical cleavages of the peptide chain; Fractionation of peptides by Sephadex or Dowex column chromatography, paper elctrophoresis or chromatography.

Horseradish peroxidase has been fractionated by preparative isoelectric focusing in a density gradient and in a layer of granulated gel using pH-3–10 and narrow-pH-range carrier ampholytes at different total enzyme loads. The resolution of peroxidase isoenzymes in preparative-layer isoelectric focusing was comparable to that obtained by analytical thin-layer isoeclectric focusing. Isoelectrically homogeneous isoenzymes could be isolated with good recovery in a single fractionation step. Despite the excellent separation of the individual isoenzymes by isoelectric focusing in gel layers, an effective purification, indicated by the absorbance ratio A403 nm/A278 nm, could not be achieved by focusing applied as a single step. By different fractionation sequences combining gel chromatography, ion-exchange chromatography, and isoelectric focusing, individual isoenzymes with a high purity and homogeneous with respect to their size and charge properties have been isolated. [ABSTRACT FROM AUTHOR]

Compound-specific stable isotope analysis ( CSIA) of individual amino acids ( AAs) has become a powerful analytical tool in trophic ecology. Heavily fractionating 'trophic' AAs (e.g., glutamic acid: Glu) provide a robust indicator of trophic transfer, while minimally fractionating 'source' AAs (e.g., phenylalanine: Phe) closely reflect the δ15N value at the base of the food web (δ15Nbaseline). Together, the CSIA- AA approach provides an unprecedented ability to disentangle the influences of δ15Nbaseline values and trophic fractionation on consumer nitrogen isotope values. Perhaps the most important assumption underlying CSIA- AA applications to trophic ecology is that trophic fractionation of Glu and Phe, and thus the trophic discrimination factor TDFGlu- Phe (Δ15 NGlu − Δ15 NPhe), is effectively constant across diverse consumer-resource relationships. To test this assumption, we conducted a comprehensive meta-analysis of controlled feeding experiments that examined individual AA trophic fractionation (Δ15 NC-D) and resulting TDFGlu- Phe values. We found tremendous variability in TDFGlu- Phe values from 0‰ to >10‰ across 70 species (317 individuals) and 88 distinct consumer-diet combinations. However, this variability appears to follow predictable patterns driven by two dominant variables: diet quality and mode of nitrogen excretion. Consumers feeding on high-quality diets (small diet-consumer AA imbalances) tend to have significantly lower TDFGlu- Phe values than consumers feeding on low-quality diets. Similarly, urea/uric acid-producing consumers also exhibit significantly lower TDFGlu- Phe values than their ammonia-producing counterparts. While these patterns are certainly not universal, together these factors likely explain many of the observed patterns of TDFGlu- Phe variability. We provide an overview of the biochemical and physiological mechanisms underpinning AA Δ15 NC-D to explain these patterns. There are several seemingly unique systems, including the remarkably consistent TDFGlu- Phe values across insect food webs and the isotopically 'invisible' trophic transfers in microbial food webs, that may provide additional insight into the influence of diet quality and nitrogen cycling on AA fractionation. In this review, we argue that to realize the full potential of CSIA- AA approaches in trophic ecology, we must embrace the variability in TDFGlu- Phe values. This likely requires developing new models of trophic transfer dynamics for some applications, including multi- TDFGlu- Phe equations that directly incorporate variability in TDFGlu- Phe value. [ABSTRACT FROM AUTHOR]

We have devised a simplified method for the purification of the bacterial initiator tRNA, tRNAfMet in amounts greater than 100 mg from 10 g of unfractionated tRNA. The purification of the normal methionine tRNA, tRNAmMet, was also achieved but with a lower yield. During the fractionation studies we identified two chromatographically separable species of tRNAfMet and two of tRNAmMet. The triplet binding assay did not differentiate between fMet-tRNAf1 and fMet-tRNAr2 or between Met-tRNAm1 and Met-tRNAm2. An anticodon containing fragment of tRNAmMet did not inhibit the charging of tRNAfMet or of tRNAmMet under conditions where it should behave as a linear sequence of nucleotides. Both tRNAfMet and tRNAmMet contain approximately one mole of £he minor nucleoside, 4-thiouridine, per mole of tRNA. In our functional tests the presence of 4-thiouridine was not necessary for the biological activity of tRNAfMet. [ABSTRACT FROM AUTHOR]