Richard Mendelsohn

Our research, which has been supported for the past twenty years by the 
National Institutes of Health, centers around applications of infrared 
spectroscopy to biophysical and biomedical problems. Three projects currently 
underway offer a good illustration of the nature of this work.

(1) We have designed and built a unique spectrometer interfaced with a 
surface balance to acquire IR spectra from monomolecular films of 
phospholipids and proteins at the air/water interface. The device has been 
used to test the "squeeze-out" hypothesis of lung surfactant function, a 
central issue in pulmonary physiology. Future work will involve precise 
determination of biomolecular conformation and orientation at the air/water 
interface.

(2) We have developed IR experiments to quantitatively describe the nature 
and location of conformational disorder in phospholipid acyl chains. This 
approach has been used to determine the physical state of the membranes in 
living cells of a microorganism. Future work will examine the molecular basis 
of homeoviscous adaptation (how biological membranes respond to environmental alterations), as well as development of additional spectra-structure correlations.

(3) We have undertaken the first IR Microscopy studies of bio-mineralizing 
tissues. Methods have been developed to determine the size and perfection 
of the hydroxyapatite crystals in diffraction limited (10 micron) samples, 
the orientation of carbonate ions which substitute for the phosphate in the 
hydroxyapatite lattice, and the relative amounts of mineral and protein in 
various tissue sites. Each of these quantities is altered during pathological 
states such as osteoporosis or vitamin D deficiency. Future work will attempt 
to develop biodiagnostic assays for the efficacy of therapeutic interventions.