Remembering David B. Knaff (1941–2016)

Abstract

David Knaff began his scientific career in the Department of Cell Physiology at the University of California, Berkeley. At Berkeley, he worked on chloroplast electron carriers such as the cytochromes and plastocyanin and applied redox potentiometry to characterize these carriers in situ. He moved to Texas Tech University where he made major contributions in the study of ferredoxin-mediated reactions with chloroplast enzymes, most notably nitrite reductase.

Site-Specific 1D and 2D IR Spectroscopy to Characterize the Conformations and Dynamics of Protein Molecular Recognition

“…Association led to an increase in the C-D frequency, consistent with a stronger interaction between Met97 and the Cu ion in the complex. A stronger interaction between the Cu ion and the axial ligand is expected to decrease the midpoint potential of Pc, 95 as is known to occur upon complexation with cyt f. 97 The IR data suggest that the functional change in Pc results from an interaction with cyt f that induces a slight contraction of the Met97-Cu bond. Altogether, the study illustrates how IR spectroscopy of C-D probes can provide molecular-level information about how the metal sites of metalloproteins are controlled by protein-protein interactions and demonstrates the utility of the high structural resolution afforded by IR spectroscopy of C-D probes for the nonperturbative characterization of localized changes in proteins.…”

“…96 While Pc has been extensively studied, how the axial Met determines the geometry and bonding of the Cu site and, moreover, how formation of the complex with cyt f might impact the metal site reactivity is not well understood. For example, complexation with cyt f was shown long ago to decrease the midpoint potential of Pc, 97 but the mechanism is unclear. One challenge is that the redox reaction of course involves both the reduced Cu(I) and oxidized Cu(II) states of Pc, but most spectroscopic methods are not able to characterize the reduced state due to its filled d 10 orbital configuration.…”