scholarly journals Chaperone-like activity of alpha-crystallin is enhanced by high-pressure treatment

2003 ◽  
Vol 370 (3) ◽  
pp. 859-866 ◽  
Author(s):  
Csaba BÖDE ◽  
Ferenc G. TÖLGYESI ◽  
László SMELLER ◽  
Karel HEREMANS ◽  
Sergiy V. AVILOV ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Small Heat Shock Protein ◽  
Total Surface Area ◽  
Key Factors ◽  
Pressure Release ◽  
Oligomeric Protein ◽  
Tryptophan Residues ◽  
Extra Activity ◽  
Vertebrate Eye ◽  
Induced Changes

α-Crystallin, an oligomeric protein in vertebrate eye lens, is a member of the small heat-shock protein family. Several papers pointed out that its chaperone-like activity could be enhanced by increasing the temperature. We demonstrate in the present study that structural perturbations by high hydrostatic pressures up to 300MPa also enhance this activity. In contrast with temperature-induced changes, the pressure-induced enhancement is reversible. After pressure release, the extra activity is lost with a relaxation time of 2.0±0.5h. Structural alterations contributing to the higher activity were studied with IR and fluorescence spectroscopy, and light-scattering measurements. The results suggest that while the secondary structure barely changes under pressure, the interactions between the subunits weaken, the oligomers dissociate, the area of accessible hydrophobic surfaces significantly increases and the environment of tryptophan residues becomes slightly more polar. It seems that structural flexibility and the total surface area of the oligomers are the key factors in the chaperone capacity, and that the increase in the chaperone activity does not require the increase in the oligomer size as was assumed previously [Burgio, Kim, Dow and Koretz (2000) Biochem. Biophys. Res. Commun. 268, 426—432]. After pressure release, the structure of subunits are reorganized relatively quickly, whereas the oligomer size reaches its original value slowly with a relaxation time of 33±4 h. In our interpretation, both the fast and slow structural rearrangements have an impact on the functional relaxation.

Sub-chronic nicotine-induced changes in regional cerebral blood volume and transversal relaxation time patterns in the rat: a magnetic resonance study

2005 ◽  
Vol 377 (3) ◽  
pp. 195-199 ◽  
Author(s):  
Laura Calderan ◽  
Christian Chiamulera ◽  
Pasquina Marzola ◽  
Paolo F. Fabene ◽  
Guido Francesco Fumagalli ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Magnetic Resonance ◽  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Regional Cerebral Blood ◽  
Magnetic Resonance Study ◽  
Chronic Nicotine ◽  
Regional Cerebral Blood Volume ◽  
Time Patterns ◽  
Induced Changes

Fluorescence Spectroscopy of the Tryptophan Microenvironment in Carcinus aestuarii Hemocyanin

2002 ◽  
Vol 57 (11-12) ◽  
pp. 1084-1091 ◽  
Author(s):  
Paolo Di Muroa ◽  
Mariano Beltramini ◽  
Peter Nikolov ◽  
Irina Petkova ◽  
Benedetto Salvato ◽  
...  
Keyword(s):  
Active Site ◽  
Oxygen Binding ◽  
Protein Matrix ◽  
Panulirus Interruptus ◽  
Time Resolved ◽  
Oligomeric Protein ◽  
Close Proximity ◽  
Tryptophan Residues ◽  
Conformational Rearrangements ◽  
Intersubunit Interactions

The steady-state and time-resolved fluorescence properties of the multitryptophan minimal subunit CaeSS2 from Carcinus aestuarii hemocyanin have been studied with the aim of probing the environment of the fluorophores within the protein matrix. Subunit a of Panulirus interruptus hemocyanin, whose X-ray structure is known, has been also studied. The results are compared with those collected with other two monomeric fractions (CaeSS1, CaeSS3) produced by dissociation of the native, oligomeric protein as well as with those of the hexameric aggregate. Three classes of tryptophan residues can be singled out by a combination of fluorescence quenching and lifetime measurements on the holo-Hc (the copper containing, oxygen binding form) and the apo-Hc (the copper-free derivative). One class of tryptophans is exposed to the protein surface. Some of these residues are proposed to be involved in the intersubunit interactions in CaeSS1 and CaeSS3 fractions whereas in CaeSS2 the protein matrix masks them. This suggests the occurrence of conformational rearrangements after detachment of the subunit from the native aggregate, which could explain the inability of CaeSS2 to reassociate. A second class of tryptophan has been correlatively assigned, by comparison with the results obtained with Panulirus interruptus hemocyanin, to residues in close proximity to the active site. The third class includes buried, active site-distant, residues.

scholarly journals The influence of activation and relaxation time on the synthesis of cordierite ceramics

2006 ◽  
Vol 71 (3) ◽  
pp. 293-301 ◽  
Author(s):  
Natasa Djordjevic ◽  
Ljubica Pavlovic
Keyword(s):  
Relaxation Time ◽  
Specific Surface ◽  
Ftir Spectroscopy ◽  
Sintering Temperature ◽  
Mechanochemical Activation ◽  
Component System ◽  
Temperature Changes ◽  
Bet Method ◽  
Cordierite Ceramics ◽  
Induced Changes

Due to its properties, cordierite, 2MgO.2Al2O3 .5SiO2, is nowadays an attractive ceramic material for various applications. Mechanochemical activation of the initial components was used in order to decrease the sintering temperature. Changes in the specific surface area of the activated components were determined by the BET method. The TG and DTA methods were used to monitor the temperature induced changes in the analyzed three-component system. The influence of the relaxation time on the activated components was analyzed by FTIR spectroscopy of both the initial components and the activated mixture after 24 h and 24 months relaxation periods. .

Unfolding and refolding of a quinone oxidoreductase: α-crystallin, a molecular chaperone, assists its reactivation

2001 ◽  
Vol 359 (3) ◽  
pp. 547-556 ◽  
Author(s):  
Shradha GOENKA ◽  
Bakthisaran RAMAN ◽  
Tangirala RAMAKRISHNA ◽  
Ch. Mohan RAO
Keyword(s):  
Tertiary Structure ◽  
Small Heat Shock Protein ◽  
Active State ◽  
Eye Lens ◽  
Quinone Oxidoreductase ◽  
Denatured State ◽  
Αb Crystallin ◽  
Partially Unfolded ◽  
Vertebrate Eye ◽  
Denatured States

α-Crystallin, a member of the small heat-shock protein family and present in vertebrate eye lens, is known to prevent the aggregation of other proteins under conditions of stress. However, its role in the reactivation of enzymes from their non-native inactive states has not been clearly demonstrated. We have studied the effect of α-crystallin on the refolding of ∊-crystallin, a quinone oxidoreductase, from its different urea-denatured states. Co-refolding ∊-crystallin from its denatured state in 2.5M urea with either calf eye lens α-crystallin or recombinant human αB-crystallin could significantly enhance its reactivation yield. αB-crystallin was found to be more efficient than αA-crystallin in chaperoning the refolding of ∊-crystallin. In order to understand the nature of the denatured state(s) of ∊-crystallin that can interact with α-crystallin, we have investigated the unfolding pathway of ∊-crystallin. We find that it unfolds through three distinct intermediates: an altered tetramer, a partially unfolded dimer, which is competent to fold back to its active state, and a partially unfolded monomer. The partially unfolded monomer is inactive, exhibits highly exposed hydrophobic surfaces and has significant secondary structural elements with little or no tertiary structure. This intermediate does not refold into the active state without assistance. α-Crystallin provides the required assistance and improves the reactivation yield several-fold.

Fatigue-induced changes in longitudinal relaxation time determined by magnetic resonance imaging

2012 ◽  
Vol 36 (6) ◽  
pp. 816-820 ◽  
Author(s):  
Kyohei Takahashi ◽  
Yukihiro Tohdoh ◽  
Takeo Matsubayashi ◽  
Vladimír Jellúš ◽  
Katsuya Maruyama
Keyword(s):  
Magnetic Resonance Imaging ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Longitudinal Relaxation Time ◽  
Resonance Imaging ◽  
Longitudinal Relaxation ◽  
Induced Changes

Morphological and elemental analysis of isolated incubated frog retina-choroid

1984 ◽  
Vol 42 ◽  
pp. 298-299
Author(s):  
B. J. Panessa-Warren ◽  
J. B. Warren ◽  
H. W. Kraner
Keyword(s):  
Elemental Analysis ◽  
Pigment Epithelium ◽  
Human Retina ◽  
Healthy Individuals ◽  
Anterior Portion ◽  
Pathological Conditions ◽  
Frog Retina ◽  
Isolated Retina ◽  
Vertebrate Eye ◽  
Retina Pigment Epithelium

Our previous studies have demonstrated that abnormally high amounts of calcium (Ca) and zinc (Zn) can be accumulated in human retina-choroid under pathological conditions and that barium (Ba), which was not detected in the eyes of healthy individuals, is deposited in the retina pigment epithelium (RPE), and to a lesser extent in the sensory retina and iris. In an attempt to understand how these cations can be accumulated in the vertebrate eye, a morphological and microanalytical study of the uptake and loss of specific cations (K, Ca,Ba,Zn) was undertaken with incubated Rana catesbiana isolated retina and RPE preparations. Large frogs (650-800 gms) were dark adapted, guillotined and their eyes enucleated in deep ruby light. The eyes were hemisected behind the ora serrata and the anterior portion of the eye removed. The eyecup was bisected along the plane of the optic disc and the two segments of retina peeled away from the RPE and incubated.

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

Drug Induced Changes in Cell Organelles

1968 ◽  
Vol 26 ◽  
pp. 110-111
Author(s):  
Sarah A. Luse
Keyword(s):  
Clinical Medicine ◽  
Cell Organelles ◽  
Riboflavin Deficiency ◽  
Drug Induced ◽  
New Era ◽  
Health And Disease ◽  
In The Beginning ◽  
Cellular Pathology ◽  
Induced Changes ◽  
The Impact

In the mid-nineteenth century Virchow revolutionized pathology by introduction of the concept of “cellular pathology”. Today, a century later, this term has increasing significance in health and disease. We now are in the beginning of a new era in pathology, one which might well be termed “organelle pathology” or “subcellular pathology”. The impact of lysosomal diseases on clinical medicine exemplifies this role of pathology of organelles in elucidation of disease today.Another aspect of cell organelles of prime importance is their pathologic alteration by drugs, toxins, hormones and malnutrition. The sensitivity of cell organelles to minute alterations in their environment offers an accurate evaluation of the site of action of drugs in the study of both function and toxicity. Examples of mitochondrial lesions include the effect of DDD on the adrenal cortex, riboflavin deficiency on liver cells, elevated blood ammonia on the neuron and some 8-aminoquinolines on myocardium.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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