Fluorescence anisotropy decay of ethidium bound to nucleosome core particles. 1. Rotational diffusion indicates an extended structure at low ionic strength

Journal Article · Tue May 28 00:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00235a024· OSTI ID:5046741

Brown, D W; Libertini, L J; Small, E W ^[1]

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1. Oregon State Univ., Corvallis (United States)

The fluorescence decay of ethidium intercalated into the DNA of nucleosome core particles increases in average lifetime from about 22 ns in H{sub 2}O to about 39 ns in D{sub 2}O. This increase, combined with the acquisiton of large amounts of data, allows measurement of anisotropy decays out to more than 350 ns. The overall slow rotational motions of the core particle may thereby be more clearly distinguished from the faster torsional motions of the DNA. In 10 mM NaCl at 20{degrees}C, the authors recover a long correlation time of 198 ns in D{sub 2}O (159 ns when corrected to a viscosity of 1.002 cP), in agreement with the value of 164 ns obtained in H{sub 2}O. These values are consistent with hydrodynamic calculations based on the expected size and shape of the hydrated particle. To support their conclusion that this long correlation time derives from Brownian rotational diffusion, they show that the value is directly proportional to the viscosity and inversely proportional to the temperature. No significant changes in the rotational correlation time are observed between 1 and 500 mM ionic strength. Below 1 mM, the particle undergoes the low-salt transition as measured by steady-state tyrosine fluorescence anisotropy. However, they observe little change in shape until the ionic strength is decreased below {approximately}0.2 mM, where the correlation time increases nearly 2-fold, indicating that the particle has opened up into an extended form. They have previously shown that the transition becomes nonreversible below 0.2 mM salt.

• OSTI ID: 5046741
• Journal Information: Biochemistry; (United States), Vol. 30:21; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CHROMATIN
ROTATIONAL STATES
NUCLEOSOMES
FLUORESCENCE SPECTROSCOPY
ANISOTROPY
BROWNIAN MOVEMENT
DIFFUSION
HEAVY WATER
HYDRODYNAMICS
EMISSION SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
FLUID MECHANICS
HYDROGEN COMPOUNDS
MECHANICS
OXYGEN COMPOUNDS
SPECTROSCOPY
WATER
550201* - Biochemistry- Tracer Techniques