Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To refine the secondary structure model of the 5' end of the bacteriophage MS2 genome, 32P-labeled MS2 RNA was partially digested with T1 RNase or with Cm-RNase and the 5'-end fragment was isolated, renatured and submitted to treatment with methoxyamine or kethoxal. The resulting modified RNA was digested with T1 RNase and the products were separated by minifingerprinting. Methoxyamine-induced modification of exposed cytidines was detected by differential mobility of modified oligonucleotides, while kethoxal-induced alteration of exposed guanosines was monitored by resistance to T1 ribonuclease digestion. The positions of the modified residues are discussed in terms of an improved secondary structure model proposed for the 5' end of the viral RNA. The structure itself is discussed in relation to sequence conservation and biological function.
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PMID:Secondary structure of the 5' end of bacteriophage MS2 RNA Methoxyamine and kethoxal modification. 11 78

A concentration of 10 mug of fluorophenylalanine per ml added to a chemically defined medium reduced by 100-fold the number of bacteriophage MS2 produced on Escherichia coli C3000 and increased the latent period. Fluorophenylalanine was most effective when added concurrent with infection. Addition of a 10-fold greater concentration of phenylalanine reversed the inhibition caused by fluorophenylalanine. Radioactive fluorophenylalanine was incorporated into the coat protein. The four phenylalanine-containing chymotryptic peptides are not equally accessible to fluorophenylalanine. Only two of the peptides are highly labeled by fluorophenylalanine. Incorporation of fluorophenylalanine decreased the specific infectivity and the rate of adsorption but did not increase the sensitivity of the whole virus to ribonuclease. MS2 ribonucleic acid (RNA) functioned as messenger RNA for the incorporation of both phenylalanine and fluorophenylalanine in a cell-free incorporating system from E. coli.
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PMID:Effect of fluorophenylalanine on bacteriophage MS2 replication. 491 28

RNA fragments of different chain length, each containing the 5'-terminal guanosine tetraphosphate (pppGp) of bacteriophage-MS2 RNA, have been isolated from partial ribonuclease digests of the viral RNA. The longest fragment overlaps with the ribosomalbinding site of the A-protein cistron. The base sequence has been established for the major part. The results directly confirm that the A-protein cistron is closest to the 5'-terminus. Its initiating (AUG) codon starts at position 130, being preceded by an untranslated sequence of 129 nucleotides.
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PMID:The leader sequence from the 5'-terminus to the A-protein initiation codon in MS2-virus RNA. 527 66

The use of electrospray ionization-quadrupole ion trap mass spectrometry for the characterization of linear oligosaccharides and N-linked protein oligosaccharide mixtures is described. Tandem mass spectrometry (MS/MS) experiments with orders higher than two offer a number of ways to enhance MS/MS spectra and to derive information not present in MS and MS2 spectra. Three such methods are presented in this paper. (a) Collisional activation of permethylated oligosaccharide molecular ions (MS2) as illustrated by maltoheptaose, produces abundant fragments from glycosidic bond cleavages which indicate composition and sequence, and weak cross-ring cleavage products which denote specific linkages within the oligosaccharide. Through the trapping and further dissociation of these fragments (MSn), cross-ring cleavage products can be confirmed and their relative abundances increased to facilitate interpretation. (b) The mechanisms of formation of two isobaric ions or ions isobaric with another ion's isotope peaks, such as those present in the MS2 spectrum of the ribonuclease B oligosaccharide GlcNAc2-Man5 can be independently established by separate MS3 experiments. (c) Ions in the MS2 spectrum, specific for individual components of an isobaric mixture, can be isolated and characterized by further stages of fragmentation. This is illustrated by two isobaric oligosaccharides from chicken ovalbumin of the composition HexNAc5Hex5. These findings indicate the utility of ion trap mass spectrometry towards the facile determination of oligosaccharide composition, sequence, branching and linkage, providing a wealth of structural information not obtainable by other individual methods of carbohydrate mass spectrometric analysis.
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PMID:Characterization of oligosaccharide composition and structure by quadrupole ion trap mass spectrometry. 933 19

Glycosylation is one of the most important posttranslational modifications affecting the functions of proteins and cell activities. Mass spectrometry (MS) has proven to be an effective tool for structural glycobiology and has helped gain an understanding of glycoprotein-mediated diseases. Although electro-spray ionization-tandem MS remains widely recognized as an effective means for oligosaccharide characterization, the hydrophilic nature of glycans has often caused the poor ionization efficiency requiring either derivatization or nanoelectrospray to improve detection sensitivity. In this report we describe the use of a chip-based infusion nanoelectrospray platform coupled with the hybrid triple quadrupole/linear ion trap for identification and characterization of glycosylation in complex mixtures. The high-mannose-type N-glycosylation in ribonuclease B was used to map the glycosylation site and obtain glycan structures. Using the chip-based nanoelectro-spray with precursor ion scanning linear ion trap MS, we were able to map the glycosylation site and obtain the glycan structures in ribonuclease B at 100 fmol/microL in a single analysis. In addition, a new, low-abundant glycoform with an additional hexose (Hex10GlcNAc2) attached to ribonuclease B was discovered. The results reported here demonstrate that the chip-based infusion nanoelectrospray ionization coupled to a quadrupole/linear ion trap platform is a valuable system, as it provides high sensitivity and stability for nanoelectrospray analysis, and allows extended acquisition time for completing precursor ion scanning and subsequent MS2 and MS3 information in a single analysis.
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PMID:Characterization of protein glycosylation using chip-based nanoelectrospray with precursor ion scanning quadrupole linear ion trap mass spectrometry. 1646 44