Lawrence W. Johnson, Professor of Chemistry at The Graduate Center and York College, is conducting research the primary aim of which is to obtain a detailed picture of the ground and excited electronic states of porphyrin molecules. Members of the porphyrin family are important components of numerous biochemical systems (e.g. heme in hemoglobin , and chlorophyll in photosynthetic reaction centers). Although spectroscopic research on porphyrins has been carried out for many years the great majority of it has been at low resolution and provided only a general view of the electronic structure of these molecules. Dr. Johnson is interested in how the electronic states of porphyrins are affected by nonplanar distortions. This research has been prompted by recent x-ray crystallographic studies of naturally occurring porphyrin-protein complexes that suggest that the proteins may alter the porphyrin's properties by inducing out-of-plane distortions. The approach to studying nonplanar porphyrin molecules is to use high resolution spectroscopic techniques such as dye lasers, low temperature (-260 C) and external electric field perturbation (Stark effect). It is anticipated that by producing detailed information on the electronic states of planar and distorted porphyrins, a better understanding will be obtained about how the associated protein in naturally occurring complexes modulates the porphyrin's properties, and consequently how it functions in biological systems.
Dr. Johnson is currently also initiating research on the dynamics and thermodynamics associated with the formation of RNA construct-peptide complexes using dual color fluorescence correlation spectrocopy (DCFCS) and single pair fluorescence resonance energy transfer (spFRET)). His research is funded by the National Institutes of Health, MBRS/SCORE.