MEDICAL HYPOTHESES AND RESEARCH
VOL. 6, No. 1/2, July 2010
C. O. Nwamba and F. C. Chilaka  Med. Hypotheses Res. 6: 25-35.
A Proposed Significance of the δ Region and its
Implications in the Mechanism of Cooperativity in
Charles O. Nwamba and Ferdinand C. Chilaka
Department of Biochemistry, University of Nigeria, Nsukka, Enugu State, Nigeria
Abstract. We propose a functional significance of the delta (δ) band in the UV-visible
spectroscopy of hemoglobin. We suggest that the formation of the delta (δ) band correlates
with the redox state of both the aromatic and sulphur-containing amino acid residues in the
environment of the haem. We suggest also that overlap of electron dense clouds, formed
from new molecular orbitals of sterically close atoms, during the transition from the deoxy-
to the oxy-conformation also contributes substantially to the phenomenon of cooperativity
in Hemoglobin. These mobile and interacting electron clouds occur on ligand binding to the
hemoglobin. We propose that oxidation that would dissipate the electron clouds would erase
the δ band since the amino acid residues involved in the δ band formation are also redox-
active and are thus good sensors to the redox environment of the Soret region.
Correspondence: Charles O. Nwamba, Department of Biochemistry, University of Nigeria,
Nsukka, Enugu State, Nigeria. Tel: 234-803 441 9424. E-Mail: charles.nwamba@unn.
or Ferdinand C. Chilaka, Department of Biochemistry, University of Nigeria, Nsukka, Enugu
State, Nigeria. Tel: 234-803 745 9903. E-Mail: email@example.com