Sense of Helix of Poly-L-histidine¹

Physical Chemical Studies on Proteins and Polypeptides

“…For example, Iizuka & Yang (94) noted large changes in the rotation PLGA (pH 7.3) with varying potassium fluoride concentration in aqueous solution. Similar results were observed by Beychok et al (95). This observation places the choice of the proper "A" values for zero helix in doubt since Yang (90) has shown that a discrepancy of about 20 per cent (for a structure having 50 per cent helix) exists between calculated hellcities using the reference values for zero helix determined with PLGA in salt free and 6M aqueous KF solutions.…”

Conformation and reactivity of DNA V. pH‐dependent conformational changes of DNA in complexes with poly‐L‐histidine: Transitions from B‐ to A‐form and to a condensed state

“…Curve~ indlc:~,e as follows: l, DNA in 10 "2 and t0 "l M Na+; 2, complex at pll 7.2 in tO -t M and |0 -a M Na÷; 3, complex t~t pH 5.2 in 10 "t M Na÷;4 and 5, poly-L-htstldlne at pH 5.8 and $.0, r~speetively. [22]. CD spectra of poly-L-histidine solutions exhibit Cotton effects in neutral and acidic pit region below 235 nm [22] [7,81.…”

“…[22]. CD spectra of poly-L-histidine solutions exhibit Cotton effects in neutral and acidic pit region below 235 nm [22] [7,81. All these polymers change the DNA conformation considerably.…”

“…The conservative behavior appears when the polypeptide exists as randon coil with very few ionized imidaTolic groups (pH ~" 7-=8) [!9--21 ! ; the A-like structure occurs above the pK-range of poly-L-histidine (pH --7) and the compact form is observed at hi~her degree of protonation of the polypeptide where it tends to form a right4tanded helical structure [22,34]. It should be empb~_~,ed, however, that ~ discussion corresponds to the dissociation coustant of the free polypeptide structure.…”

Glutathion-Peroxidase, III. Spektrale Charakteristika und Versuche zum Reaktionsmechanismus

“…Zur Deutung des langwelligen (> 225 nm) CD-Spektrums der GSH-Peroxidase müssen die Beiträge der Seitenkettenchromophore der Aminosäuren L-Cystin, L-Phenylalanin, L-Tryptophan, L-Tyrosin und L-Histidin diskutiert werden 18 : Histidinreste können kaum zur Erklärung des CD-Spektrums der GSH-Peroxidase zwischen 250 und 300 nm herangezogen werden, da der langwelligste CoTTON-EfTekt von Poly-L-histidin bei 222 nm liegt 19 . Dem Phenylalanin dürfte ebenfalls eine untergeordnete Bedeutung zukommen, da die COTTON-Effekte des Aromatenchromophors gering sind 20 · 21 .…”