{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,14]],"date-time":"2025-11-14T13:07:23Z","timestamp":1763125643210,"version":"3.45.0"},"reference-count":55,"publisher":"Wiley","issue":"11","license":[{"start":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T00:00:00Z","timestamp":1760313600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Protein Science"],"published-print":{"date-parts":[[2025,11]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    The effect of pH (between pH\u20097.0 and 0.0) on the spectroscopic properties of ferric and ferrous derivatives of horse heart cytochrome\n                    <jats:italic>c<\/jats:italic>\n                    (hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(III) and hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(II), respectively) in 1.0M phosphate buffer is reported. This study further deepens the investigation of spectroscopic properties of a heme\u2010protein to very low pH (i.e., pH\u2009\u2248\u20090) showing relevant pH\u2010dependent variations of the heme surroundings, involving the heme\u2010Fe atom coordination. For both hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(III) and hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(II) a severe weakening of the Fe\u2010Met80 has been detected with a similar p\n                    <jats:italic>K<\/jats:italic>\n                    <jats:sub>a<\/jats:sub>\n                    , ranging between 2.5 and 3.0, suggesting a very small effect on the free energy for the protonation of this bond from the oxidation state of the heme's iron. Therefore, in the presence of either CO or NO, it has been possible to detect the formation at acid pH of hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(II)\u2010CO and hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(II)\u2010NO forms. On the other hand, the free energy for the protonation of the His18\u2010Fe proximal bond seems dependent on the oxidation state of the heme's iron, since a p\n                    <jats:italic>K<\/jats:italic>\n                    <jats:sub>a<\/jats:sub>\n                    \u2009\u2248\u20090.2 is observed for its cleavage in the hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(III) species, while this bond appears still intact in hhcyt\n                    <jats:italic>c<\/jats:italic>\n                    \u2010Fe(II) even at pH\u2009\u2248\u20090. Since during patho\u2010physiological conditions cytochrome\n                    <jats:italic>c<\/jats:italic>\n                    may experience dramatic pH changes of the surroundings, this information turns out of the utmost relevance to explore mechanistic insights of pathological processes, such as redox unbalance and mitochondrial dysfunction, linked to cytochrome\n                    <jats:italic>c<\/jats:italic>\n                    alterations (e.g., neurodegeneration), for which effective modulation of the cytochrome\n                    <jats:italic>c<\/jats:italic>\n                    properties may be of therapeutic relevance.\n                  <\/jats:p>","DOI":"10.1002\/pro.70233","type":"journal-article","created":{"date-parts":[[2025,10,14]],"date-time":"2025-10-14T01:56:30Z","timestamp":1760406990000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Proton\u2010linked effects on the axial coordination in ferric and ferrous horse heart cytochrome\n                    <i>c<\/i>"],"prefix":"10.1002","volume":"34","author":[{"given":"Federico","family":"Sebastiani","sequence":"first","affiliation":[{"name":"Dipartimento di Chimica \u201cUgo Schiff\u201d, DICUS Universit\u00e0 di Firenze  Sesto Fiorentino Italy"},{"name":"The European Laboratory for Non\u2010Linear Spectroscopy (LENS)  Sesto Fiorentino (FI) Italy"},{"name":"INSTM Research Unit of Firenze  Sesto Fiorentino Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alessio","family":"Bocedi","sequence":"additional","affiliation":[{"name":"Dipartimento di Scienze e Tecnologie chimiche Universit\u00e0 di Roma Tor Vergata  Rome Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Giovanna","family":"De Simone","sequence":"additional","affiliation":[{"name":"Dipartimento di Scienze Universit\u00e0 Roma Tre  Rome 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