Differing structural characteristics of molten globule intermediate of peanut lectin in urea and guanidine-HCl

The refolding course and intermediate of guanidine hydrochloride (GuHCl)-denatured arginine kinase (AK) were studied in terms of enzymatic activity, intrinsic fluorescence, 1-anilino-8-naphthalenesulfonte (ANS) fluorescence, and far-UV circular dichroism (CD). During AK refolding, the fluorescence intensity increased with a significantly blue shift of the emission maximum. The molar ellipticity of CD increased to close to that of native AK, as compared with the fully unfolded AK. In the AK refolding process, 2 refolding intermediates were observed at the concentration ranges of 0.8–1.0 mol/L and 0.3–0.5 mol GuHCl/L. The peak position of the fluorescence emission and the secondary structure of these conformation states remained roughly unchanged. The tryptophan fluorescence intensity increased a little. However, the ANS fluorescence intensity significantly increased, as compared with both the native and the fully unfolded states. The first refolding intermediate at the range of 0.8–1.0 mol GuHCl/L concentration represented a typical "pre-molten globule state structure" with inactivity. The second one, at the range of 0.3–0.5 mol GuHCl/L concentration, shared many structural characteristics of native AK, including its secondary and tertiary structure, and regained its catalytic function, although its activity was lower than that of native AK. The present results suggest that during the refolding of GuHCl-denatured AK there are at least 2 refolding intermediates; as well, the results provide direct evidence for the hierarchical mechanism of protein folding.Key words: arginine kinase, guanidine-denatured, refolding, intermediate, molten globule state.

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The human androgen receptor AF1 transactivation domain: interactions with transcription factor IIF and molten-globule-like structural characteristics

Biochemical Society Transactions ◽

10.1042/bst0341054 ◽

2006 ◽

Vol 34 (6) ◽

pp. 1054-1057 ◽

Cited By ~ 20

Author(s):

D.N. Lavery ◽

I.J. McEwan

Keyword(s):

Transcription Factor ◽

Androgen Receptor ◽

Protein Interactions ◽

Structural Characteristics ◽

Molten Globule ◽

Transactivation Domain ◽

Protein Protein Interactions ◽

Induced Folding ◽

Transcription Factor Iif ◽

Structural Aspects

The AR (androgen receptor) is a ligand-activated transcription factor and member of the steroid receptor superfamily. The AR responds to the ligands testosterone and dihydrotestosterone and activates multiple downstream genes required in development and reproduction. During the events of transactivation, the AR makes specific protein–protein interactions with several basal transcription factors such as TBP (TATA-box-binding protein) and TFIIF (transcription factor IIF). These interactions occur predominantly within a defined region termed AF1 (activation function-1) located within the highly disordered N-terminal domain of the receptor. Our focus is on the structural aspects of AF1 and how this flexible and disordered domain generates functional interactions with regulators of transcription. Our working hypothesis is that AR-AF1 domain exhibits induced folding when contacted by transcription regulators (such as TFIIF) into a more compact and ‘active’ conformation, enabling further co-regulator recruitment and ultimately transcription. Structural flexibility and intrinsic disorder of AR-AF1 were studied using predictive algorithms and fluorescence spectroscopy under different experimental conditions and the results revealed this domain retains characteristics indicative of molten-globule or pre-molten-globule-like structures. We hypothesize that this partially folded intermediate state is important for, and enables the AF1 domain to make, multiple protein–protein interactions. The structural aspects of AR-AF1 and interactions with TFIIF are discussed.

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A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055904 ◽

1982 ◽

Vol 40 ◽

pp. 722-723 ◽

Cited By ~ 1

Author(s):

R. Gronsky

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

High Resolution ◽

Computer Simulations ◽

Structural Characteristics ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

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SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109422 ◽

1978 ◽

Vol 36 (1) ◽

pp. 456-457

Author(s):

V. Annamalai ◽

L.E. Murr

Keyword(s):

Structural Characteristics ◽

Secondary Electron Emission ◽

Copper Deposit ◽

Reaction Rates ◽

Sem Analysis ◽

Experimental Conditions ◽

Major Drawback ◽

Emission Mode ◽

Scrap Iron ◽

Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

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Use of 2½ D imaging in analysis of NiTi martensite

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110192 ◽

1978 ◽

Vol 36 (1) ◽

pp. 610-611

Author(s):

G. M. Michal

Keyword(s):

Memory Effect ◽

Monoclinic Phase ◽

Reaction Path ◽

Structural Characteristics ◽

Salient Feature ◽

Martensite Phase ◽

Orientation Relationships ◽

Low Symmetry ◽

Hydride Phases ◽

Unusual Shape

Several TEM investigations have attempted to correlate the structural characteristics to the unusual shape memory effect in NiTi, the consensus being the essence of the memory effect is ostensible manifest in the structure of NiTi transforming martensitic- ally from a B2 ordered lattice to a low temperature monoclinic phase. Commensurate with the low symmetry of the martensite phase, many variants may form from the B2 lattice explaining the very complex transformed microstructure. The microstructure may also be complicated by the enhanced formation of oxide or hydride phases and precipitation of intermetallic compounds by electron beam exposure. Variants are typically found in selfaccommodation groups with members of a group internally twinned and the twins themselves are often observed to be internally twinned. Often the most salient feature of a group of variants is their close clustering around a given orientation. Analysis of such orientation relationships may be a key to determining the nature of the reaction path that gives the transformation its apparently perfect reversibility.

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Use of light microscopy in the qualitative and quantitative study of liquid crystalline order

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121727 ◽

1992 ◽

Vol 50 (1) ◽

pp. 264-265

Author(s):

Christopher Viney

Keyword(s):

Light Microscopy ◽

Liquid Crystalline ◽

Structural Characteristics ◽

Molecular Order ◽

Liquid Crystalline Phases ◽

Convenient Technique ◽

Liquid Crystalline Materials ◽

Transparent Windows

Light microscopy is a convenient technique for characterizing molecular order in fluid liquid crystalline materials. Microstructures can usually be observed under the actual conditions that promote the formation of liquid crystalline phases, whether or not a solvent is required, and at temperatures that can range from the boiling point of nitrogen to 600°C. It is relatively easy to produce specimens that are sufficiently thin and flat, simply by confining a droplet between glass cover slides. Specimens do not need to be conducting, and they do not have to be maintained in a vacuum. Drybox or other controlled environmental conditions can be maintained in a sealed chamber equipped with transparent windows; some heating/ freezing stages can be used for this purpose. It is relatively easy to construct a modified stage so that the generation and relaxation of global molecular order can be observed while specimens are being sheared, simulating flow conditions that exist during processing. Also, light only rarely affects the chemical composition or molecular weight distribution of the sample. Because little or no processing is required after collecting the sample, one can be confident that biologically derived materials will reveal many of their in vivo structural characteristics, even though microscopy is performed in vitro.

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