New methods for sedimentation and diffusion analysis of macromolecular structure

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:7044828

Demeler, B

Methods are presented to acquire data from analytical ultracentrifugation experiments by computer using the absorption optical scanning system of the Beckman Model-E ultracentrifuge. A computer program was written which analyzes sedimentation velocity experiments by the van Holde-Weischet method and the second moment method. The van Holde-Weischet method allows a high resolution analysis of sedimentation velocity data by eliminating the effects of diffusion on the shape of the moving boundary to provide sedimentation coefficients for a heterogeneous composition of a sample. The second moment method obtains the sedimentation coefficient by calculating the second moment point, by which the sedimentation coefficient is defined. A program was written for the acquisition of data to measure diffusion coefficients from quasi elastic light scattering experiments with a Langely Ford correlator. The analysis of autocorrelation spectra from light scattering experiments is performed by the Levenberg-Marquardt method, which allows fitting of data to nonlinear models. The development of the PPOL-1 208-n series of plasmids and of the miniplasmid pMX is described. These plasmids were designed to allow studies of in vitro transcription and chromatin structure after reconstitution with histones. Sedimentation data are presented which suggests a new method for rapid estimation of the sedimentation coefficient at zero concentration for molecules which show a concentration dependency of the sedimentation coefficient. This is accomplished by linearly extrapolating van Holde-Weischet distributions to zero concentration. Diffusion data for this plasmid DNA is used to demonstrate the feasibility of the multicomponent analysis. Sedimentation measurements were carried out on reconstituted chromatin. The programs were used to demonstrate significant changes in chromatin structure upon ethidium bromide binding.

• Research Organization: Oregon State Univ., Corvallis, OR (United States)
• OSTI ID: 7044828
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
CHROMATIN
DIFFUSION
SEDIMENTATION
PLASMIDS
ULTRACENTRIFUGATION
DATA ACQUISITION
DATA ANALYSIS
MOLECULAR STRUCTURE
CELL CONSTITUENTS
CENTRIFUGATION
SEPARATION PROCESSES
400102* - Chemical & Spectral Procedures
550200 - Biochemistry