PubMed · 4623017
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R Jedrzejewski. 1972-03-16. [Parenteral hyperalimentation].. https://pubmed.ncbi.nlm.nih.gov/4623017/
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Amino acid (AA) profiles from body fluids such as blood and urine are clinical indicators for diagnosing metabolic and hepatic diseases. Current quantitative methods, such as liquid chromatography-mass spectrometry (LC-MS) with isotopically labelled internal standards (ISs), are costly and technically demanding. This study proposes a cost-efficient alternative using structural isomers as ISs in a direct liquid infusion (DLI) tandem mass spectrometry (MS/MS) approach. The method leverages chimeric spectra and fragment intensity ratios to quantify AAs, demonstrating high linearity and precision even with a 3D ion trap mass analyser. This approach offers a viable strategy for AA quantification in preventive medicine, particularly for screening metabolic diseases such as phenylketonuria, diabetes, and liver dysfunction.
The human immunodeficiency virus type 1 and type 2 (HIV-1 and HIV-2) reverse transcriptases (RTs) are evolutionary related. To study the effect of homologous sequence replacements on polymerase function and to map the determinants of the lack of susceptibility of HIV-2 RT to nonnucleoside drugs, a series of chimeric HIV-1/HIV-2 RTs were constructed. Analysis of the chimeric RTs showed that wild-type levels of RNA-dependent DNA polymerase activity were retained when both finger and palm subdomains were exchanged as a unit between the two parental RTs. Analysis of enzymatically active chimeras for inhibition by the thiobenzimidazolone derivative TIBO R82150 showed that a segment of HIV-2 RT at 212-250, when placed in the HIV-1 RT context, conferred a 40-fold decrease in susceptibility to TIBO R82150. Site-directed mutagenesis of this segment found Tyr227 to be a key residue in this segment for the natural resistance of HIV-2 RT to TIBO R82150.
IS10 transposase mediates end pairing, donor cleavage (or excision) and strand transfer reactions in IS10/Tn10 transposition. Details of how this multi-functional protein mediates these various steps have not been determined. We have used a genetic approach to help define structure-function relationships for IS10 transposase. IS10 transposase mutants that failed to form an excised transposon fragment in vivo and conferred a dominant-negative phenotype were isolated. Mutants with these properties were expected to be defective in catalysis and/or steps preceding donor cleavage. A total of seven mutants were identified, the corresponding proteins were purified and their activities assessed in vitro. Mutant EK292 was found to form wild-type levels of paired end complex, an early intermediate in the reaction, but to be defective in both donor cleavage and strand transfer. This phenotype suggests that E292 comprises part of a catalytic region. Mutants RH119, SF120 and RQ296 formed aberrant paired end complexes, indicating a defect in a step(s) preceding donor cleavage. Mutants WR98, IS101, and AV162 were found to promote donor cleavage in vitro but not strand transfer. For IS101 and AV162 the defect in strand transfer may be related to instability of excision complexes. Finally, the observation that IS101, RH119 and AV162 were greatly suppressed by Mn2+ suggests that these mutations have an effect on Mg2+ interactions with transposase.