Thermal unfolding of myosin rod and light meromyosin: circular dichroism and tryptophan fluorescence studies

Biochemistry ◽  
1989 ◽  
Vol 28 (8) ◽  
pp. 3498-3502 ◽  
Author(s):  
Lan King ◽  
Sherwin S. Lehrer
Keyword(s):  
Circular Dichroism ◽  
Tryptophan Fluorescence ◽  
Thermal Unfolding ◽  
Fluorescence Studies ◽  
Circular Dichroïsm ◽  
Myosin Rod

scholarly journals Conformational dynamics of estrogen receptors α and β as revealed by intrinsic tryptophan fluorescence and circular dichroism

2005 ◽  
Vol 35 (2) ◽  
pp. 211-223 ◽  
Author(s):  
S K Nair ◽  
T J Thomas ◽  
N J Greenfield ◽  
A Chen ◽  
H He ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Estrogen Receptors ◽  
Conformational Dynamics ◽  
Tryptophan Fluorescence ◽  
Thermal Unfolding ◽  
Force Microscopy ◽  
Estrogen Response ◽  
Intrinsic Tryptophan Fluorescence ◽  
Partially Unfolded ◽  
Circular Dichroïsm

Estrogen receptors (ERα and ERβ) are ligand-activated nuclear receptors that mediate the action of estrogens. These receptors activate transcription by similar mechanism(s), although the overall amino acid sequence identity is only 47%. In order to compare the structural and conformational features of ERα and ERβ, we monitored their intrinsic tryptophan fluorescence during thermal unfolding. The 50% unfolding temperatures (TM) of ERα and ERβ were 39±1 and 40±2°C, respectively. Estradiol had no significant effect on the TM of ERα or ERβ. In contrast, binding of the estrogen-response element increased the TM of ERα and ERβ by 10 °C. Thermal unfolding of estradiol-bound ERα and ligand-free ERβ showed two-step transitions, with the formation of intermediates that were stable between 36–48 and 34–42°C, respectively. We confirmed the presence of intermediate states during thermal unfolding by circular dichroism spectroscopy. Atomic force microscopy showed that the ERβ intermediate consisted of discrete globular particles, whereas the ERα intermediate showed a speckled appearance, with sparse well-defined particles. Fluorescence-quenching studies showed the presence of two classes of tryptophan in unliganded ERα and ERβ. Binding of estradiol to ERβ exposed its tryptophans, whereas estradiol reduced the accessibility of the tryptophans of ERα. Our results illustrate the differential effects of ligands on the unfolding of ERα and ERβ, and identify partially unfolded intermediates. Differences in the conformational flexibility and stability of ERα and ERβ may represent functional differences of ligand-bound ERs in recruiting coactivator proteins and initiating transcription.

scholarly journals The effects of Ca2+ and Cd2+ on the secondary and tertiary structure of bovine testis calmodulin. A circular-dichroism study

1986 ◽  
Vol 238 (2) ◽  
pp. 485-490 ◽  
Author(s):  
S R Martin ◽  
P M Bayley
Keyword(s):  
Circular Dichroism ◽  
Conformational Changes ◽  
Metal Ion ◽  
Tertiary Structure ◽  
Thermal Unfolding ◽  
Apparent Effect ◽  
Thermally Induced ◽  
Circular Dichroïsm ◽  
Secondary And Tertiary Structure

Near-u.v. and far-u.v. c.d. spectra of bovine testis calmodulin and its tryptic fragments (TR1C, N-terminal half, residues 1-77, and TR2C, C-terminal half, residues 78-148) were recorded in metal-ion-free buffer and in the presence of saturating concentrations of Ca2+ or Cd2+ under a range of different solvent conditions. The results show the following: if there is any interaction between the N-terminal and C-terminal halves of calmodulin, it has not apparent effect on the secondary or tertiary structure of either half; the conformational changes induced by Ca2+ or Cd2+ are substantially greater in TR2C than they are in TR1C; the presence of Ca2+ or Cd2+ confers considerable stability with respect to urea-induced denaturation, both for the whole molecule and for either of the tryptic fragments; a thermally induced transition occurs in whole calmodulin at temperatures substantially below the temperature of major thermal unfolding, both in the presence and in the absence of added metal ion; the effects of Cd2+ are identical with those of Ca2+ under all conditions studied.

Circular dichroism and fluorescence studies to probe the conformational properties of Rhus vernicifera laccase

1992 ◽  
Vol 193 (2) ◽  
pp. 237-243 ◽  
Author(s):  
Fernanda Ricchelli ◽  
Mariano Beltramini ◽  
Luigi Bubacco ◽  
Benedetto Salvato ◽  
Bruno Filippi
Keyword(s):  
Circular Dichroism ◽  
Fluorescence Studies ◽  
Conformational Properties ◽  
Rhus Vernicifera ◽  
Circular Dichroïsm

Structural Changes of ?-Lactoglobulin during Thermal Unfolding and Refolding ? An FT-IR and Circular Dichroism Study

2005 ◽  
Vol 24 (1) ◽  
pp. 27-35 ◽  
Author(s):  
C. Bhattacharjee ◽  
S. Saha ◽  
A. Biswas ◽  
M. Kundu ◽  
L. Ghosh ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Structural Changes ◽  
Thermal Unfolding ◽  
Ft Ir ◽  
Circular Dichroïsm
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