Spectroscopic and kinetic aspects of Elephas maximus hemoglobin

Abstract

In comparison with myoglobin and human and Glycera dibranchiata hemoglobins, the heme distal side amino acid exchanges within the heme environment of elephant tetrameric hemoglobin (Hbe) only slightly affect the electronic and ESR spectra of Hbe(III) and Hbe(II) derivatives, several of which were prepared and characterized by optical and ESR spectroscopy. Addition of 2,3‐bisphosphoglycerate [Gri(2,3)P2] or inositol hexakisphosphate to Hbe(II)NO causes tension in the Fe‐N(proximal His) bond, although the behaviour differs in detail from that of HbA(II)NO. There are two equilibrium states of Hbe having significantly different kinetics for the Hbe(III) Hbe(II) reaction of Hbe(III)NO. This autoreduction occurs in the form of two parallel processes, which collapse into one intermediate rate in the presence of Gri(2,3)P2. The temperature dependences of the rates enable deduction of H0 and S0 for the linked equilibrium, and yield liner Eyring plots for Hbe(III)NO, from which activation parameters were estimated on the basis of a previously described mechanism.

Kinetic and spectroscopic studies of haemoglobin and myoglobin from Urechis caupo. Distal residue effects

“…The Fe(III) spectra of human HbA, horse Mb, sperm-whale Mb and elephant Hbe appear to be quite similar to one another; these proteins each possess a distal histidine residue (Braunitzer et al, 1982;Dickerson & Geis, 1983;Mabbutt & Wright, 1985;Stephanos & Addison, 1990). Quantitative comparison of the Fe(III) spectra of the distal histidine-containing proteins, which appear to be six-co-ordinate in their Fe(III) state (Antonini & Brunori, 1971, pp. (Eaton & Hochstrasser, 1967, 1968 (Bickar et al, 1984).…”

Low-Temperature Thermochromism Marks a Change in Coordination for the Metal Ion in Manganese Superoxide Dismutase

“…Variable temperature studies of structure, function, and spectra can reveal some of the dynamical aspects of the biological active site (Hopfield, 1987;Fraunfelder et al, 1991). VT optical spectroscopy (Chance, 1993;Austin & Erramilli, 1995) has been used to study the thermal behavior of protein complexes involved in electron transfer (Woodruff et al, 1984;Nocek et al, 1990;Gunner & Dutton, 1989) and ligand binding (Neya et al, 1985a,b;Stephanos & Addison, 1990). Metalloenzyme complexes can be particularly interesting for these studies because of the structural information contained in the ligand field spectra.…”

Human serum albumin complexes with chlorophyll and chlorophyllin

“…The values of the binding constants K were obtained according to the methods described by Stephanos23 and/or Zhong 24. By assuming that there is only one type of interaction between pigment and protein in aqueous solution, Eqs.…”

“…(4) and (5), Eq. (6) can be deduced: Thus, the double reciprocal plot of 1/( A − A 0 ) vs. 1/ C Pigment (or 1/[Pigment]) is linear, and the binding constants ( K ) can be estimated from the ratio of the intercept to the slope 23, 24…”