PMC:7795856 / 10292-11730 JSONTXT

{"project":"LitCovid-PubTator","denotations":[{"id":"222","span":{"begin":181,"end":184},"obj":"Gene"},{"id":"223","span":{"begin":1304,"end":1307},"obj":"Gene"},{"id":"224","span":{"begin":46,"end":53},"obj":"Chemical"},{"id":"225","span":{"begin":1427,"end":1437},"obj":"Chemical"}],"attributes":[{"id":"A222","pred":"tao:has_database_id","subj":"222","obj":"Gene:134864"},{"id":"A223","pred":"tao:has_database_id","subj":"223","obj":"Gene:134864"},{"id":"A224","pred":"tao:has_database_id","subj":"224","obj":"MESH:D019343"},{"id":"A225","pred":"tao:has_database_id","subj":"225","obj":"MESH:D008715"}],"namespaces":[{"prefix":"Tax","uri":"https://www.ncbi.nlm.nih.gov/taxonomy/"},{"prefix":"MESH","uri":"https://id.nlm.nih.gov/mesh/"},{"prefix":"Gene","uri":"https://www.ncbi.nlm.nih.gov/gene/"},{"prefix":"CVCL","uri":"https://web.expasy.org/cellosaurus/CVCL_"}],"text":"The protein solutions were dialyzed against a citrate buffer at pH 3.0 and subsequently applied to a strong cation exchange (CEX) column, which resulted in a bound fraction for PAS-Tα1, whereas both a flow-through fraction and a bound fraction were observed for Tα1-PAS (Figure 2). Electrospray ionization mass spectrometry (ESI-MS) analysis of Tα1-PAS in the flow-through revealed a molecular mass of 52,734.56 Da (Figure 2a), which exactly matches the calculated mass for the N-terminally acetylated gene product (52,734.56 Da). In this case, the start methionine of Tα1-PAS (followed by a Ser residue) was fully processed, presumably by the bacterial methionine aminopeptidase [39], then followed by N-terminal acetylation via RimJ. In contrast, the column-bound peptide fraction, which was eluted using a salt concentration gradient, showed a molecular mass of 52,692.38 Da (Figure 2b), which corresponds to the calculated mass for the non-acetylated processed polypeptide (52,692.54 Da) accompanied by some minor peaks below 40 kDa, most likely due to residual host cell impurities. Accordingly, this CEX step enabled separation of the desired N-acetylated Tα1-PAS from its non-acetylated precursor as a result of a single charge difference. In comparison, the fully column-bound non-acetylated PAS-Tα1 showed a single molecular mass of 52,789.8 Da (Figure 3) corresponding to the intact peptide, again, lacking the start methionine."}

{"project":"LitCovid-sentences","denotations":[{"id":"T64","span":{"begin":0,"end":281},"obj":"Sentence"},{"id":"T65","span":{"begin":282,"end":530},"obj":"Sentence"},{"id":"T66","span":{"begin":531,"end":735},"obj":"Sentence"},{"id":"T67","span":{"begin":736,"end":1087},"obj":"Sentence"},{"id":"T68","span":{"begin":1088,"end":1246},"obj":"Sentence"},{"id":"T69","span":{"begin":1247,"end":1438},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"The protein solutions were dialyzed against a citrate buffer at pH 3.0 and subsequently applied to a strong cation exchange (CEX) column, which resulted in a bound fraction for PAS-Tα1, whereas both a flow-through fraction and a bound fraction were observed for Tα1-PAS (Figure 2). Electrospray ionization mass spectrometry (ESI-MS) analysis of Tα1-PAS in the flow-through revealed a molecular mass of 52,734.56 Da (Figure 2a), which exactly matches the calculated mass for the N-terminally acetylated gene product (52,734.56 Da). In this case, the start methionine of Tα1-PAS (followed by a Ser residue) was fully processed, presumably by the bacterial methionine aminopeptidase [39], then followed by N-terminal acetylation via RimJ. In contrast, the column-bound peptide fraction, which was eluted using a salt concentration gradient, showed a molecular mass of 52,692.38 Da (Figure 2b), which corresponds to the calculated mass for the non-acetylated processed polypeptide (52,692.54 Da) accompanied by some minor peaks below 40 kDa, most likely due to residual host cell impurities. Accordingly, this CEX step enabled separation of the desired N-acetylated Tα1-PAS from its non-acetylated precursor as a result of a single charge difference. In comparison, the fully column-bound non-acetylated PAS-Tα1 showed a single molecular mass of 52,789.8 Da (Figure 3) corresponding to the intact peptide, again, lacking the start methionine."}