Armen P. Sarvazyan
Dept. of Chem., Rutgers Univ., New Brunswick, NJ 08903
A great potential of acoustics in the thermodynamic characterization of biomolecular systems, studies of conformational transitions and hydration of proteins and nucleic acids and drug--biopolimer interactions has been revealed in the last decade mainly due to advances in the instrumentation for ultrasonic measurements in small volumes of liquids. The methods and devices reviewed in this talk are based upon the fixed path interferometer method, also known as a ``resonator method.'' It is the only method which can provide measurements of ultrasound velocity and attenuation in the sample volume of the order of 10--100 microliters with sufficient precision. The requirement of small sample volume is a major precondition for applicability of the method to the most of the problems in biomolecular studies. Different types of resonators will be described in detail including a new type of micro-volume cylindrical standing wave resonators with a chamber volume of about 3 microliters. The electronic circuits for high precision measurement using acoustical resonators are usually based on the phase-locked loop which provides the oscillation in the system at the chosen resonance. Fields of applications and prospects of future development of instrumentation will be reviewed. [sup a)]Permanent address: Inst. of Theoret. and Exp. Biophys., Russian Acad. of Sci.