scholarly journals Effect of temperature on the secondary structure of β-lactoglobulin at pH 6.7, as determined by CD and IR spectroscopy: a test of the molten globule hypothesis

1997 ◽  
Vol 324 (1) ◽  
pp. 341-346 ◽  
Author(s):  
Xiao Lin QI ◽  
Carl HOLT ◽  
David MCNULTY ◽  
David T. CLARKE ◽  
Sharon BROWNLOW ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Molten Globule ◽  
Cd Spectroscopy ◽  
Helical Conformation ◽  
Effect Of Temperature ◽  
Sheet Structure ◽  
Good Signal ◽  
Increasing Temperature ◽  
Β Lactoglobulin ◽  
Β Sheet

Previous CD measurements of changes in the conformation of β-lactoglobulin at neutral pH as a function of temperature indicated the formation of a molten globule state above approx. 70 °C. New CD measurements are reported at temperatures up to 80 °C with an instrument on the Daresbury synchrotron radiation source which gives spectra of good signal-to-noise ratio down to 170 nm. IR spectra were recorded up to 94.8 °C with a ZnSe circle cell and a single simplified model of the substructure of the amide I′ band was used to give the fractional contents of β-sheet structure unambiguously and independently of the CD spectroscopy. The results of both techniques, however, were in agreement in showing a progressive loss of β-sheet structure with increasing temperature, beginning below the denaturation temperature. Nevertheless, the CD spectroscopy showed a fairly abrupt loss of virtually all the helical conformation at approx. 65 °C. Comparison of the present results with other studies on the molten globule formed at acid pH in the lipocalin family suggests that above 65 °C a partly unfolded state is formed, possibly by destabilization of the intermolecular β-strand I and the loss of the main helix, but it is not a classical molten globule transition.

Effect of curcumin on amyloidogenic property of molten globule-like intermediate state of 2,5-diketo-d-gluconate reductase A

2009 ◽  
Vol 390 (10) ◽  
Author(s):  
Nandini Sarkar ◽  
Abhay Narain Singh ◽  
Vikash Kumar Dubey
Keyword(s):  
Protein Concentration ◽  
Molten Globule ◽  
Molar Ratio ◽  
Amyloid Formation ◽  
Molten Globule State ◽  
Force Microscopy ◽  
Atomic Force ◽  
Sheet Structure ◽  
Amyloid Diseases ◽  
Β Sheet

Abstract We identified a molten globule-like intermediate of 2,5-diketo-d-gluconate reductase A (DKGR) at pH 2.5, which has a prominent β-sheet structure. The molten globule state of the protein shows amyloidogenic property >50 μm protein concentration. Interestingly, a 1:1 molar ratio of curcumin prevents amyloid formation as shown by the Thioflavin-T assay and atomic force microscopy. To the best of our knowledge, this is the first report on amyloid formation by an (α/β)8-barrel protein. The results presented here indicate that the molten globule state has an important role in amyloid formation and potential application of curcumin in protein biotechnology as well as therapeutics against amyloid diseases.

Secondary Structure of Decorin-Derived Peptides in Solution

MRS Advances ◽  
2016 ◽  
Vol 1 (27) ◽  
pp. 1965-1970
Author(s):  
Axel T. Neffe ◽  
Stefania Federico ◽  
Andreas Lendlein
Keyword(s):  
Crystal Structure ◽  
Outer Surface ◽  
Cd Spectroscopy ◽  
Helical Conformation ◽  
Structural Elements ◽  
Original Sequence ◽  
X Ray ◽  
Inner Surface ◽  
Β Sheet ◽  
Secondary Structural Elements

ABSTRACTDecorin is a small leucine-rich repeat proteoglycan supporting collagen fibril formation by controlling the rate of collagen fibrillogenesis and fibril dimensions. Peptides derived from the inner surface of decorin have been shown to bind to collagen, while peptides derived from the outer surface do not display such binding affinity. As typical secondary structural elements such as β-sheets and α-helical regions were found in the decorin X-ray crystal structure, here it was investigated by Circular Dichroism (CD) spectroscopy in solution, whether the same structural elements can be found in the derived peptides. Here it is shown that the peptide derived from decorin’s outer surface has the propensity to adopt helical conformation, as it was found in the crystal structure. The results were more pronounced in 80 vol% TFE solution, which led to an increase in the number as well as the length of helices. In contrast, peptides derived from the inner surface had a higher tendency to adopt β-sheet conformation, also in TFE, which corresponds to the conformation of the original sequence in the crystal structure of decorin. This suggests that the peptides derived from decorin adopt the structures present in the native protein.

scholarly journals Synthetic putative transmembrane region of minimal potassium channel protein (minK) adopts an α-helical conformation in phospholipid membranes

1997 ◽  
Vol 325 (2) ◽  
pp. 475-479 ◽  
Author(s):  
Eric A. J. MERCER ◽  
Geoffrey W. ABBOTT ◽  
Stephen P. BRAZIER ◽  
Bala RAMESH ◽  
Parvez I. HARIS ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Potassium Channel ◽  
Transmembrane Domain ◽  
Cd Spectroscopy ◽  
Helical Conformation ◽  
Phospholipid Membranes ◽  
Transmembrane Region ◽  
Aqueous Buffer ◽  
Channel Protein ◽  
Β Sheet

Minimal potassium channel protein (minK) is a potassium channel protein consisting of 130 amino acids, possessing just one putative transmembrane domain. In this study we have synthesized a peptide with the amino acid sequence RDDSKLEALYILMVLGFFGFFTLGIMLSYI, containing the putative transmembrane region of minK, and analysed its secondary structure by using Fourier-transform IR and CD spectroscopy. The peptide was virtually insoluble in aqueous buffer, forming intermolecular β-sheet aggregates. On attempted incorporation of the peptide into phospholipid membranes with a method involving dialysis, the peptide adopted a predominantly intermolecular β-sheet conformation identical with that of the peptide in aqueous buffer, in agreement with a previous report [Horvàth, Heimburg, Kovachev, Findlay, Hideg and Marsh, (1995) Biochemistry 34, 3893–3898]. However, by using an alternative method of incorporating the peptide into phospholipid membranes we found that the peptide adopted a predominantly α-helical conformation, a finding consistent with various proposed structural models. These observed differences in secondary structure are due to artifacts of aggregation of the peptide before incorporation into lipid.

Crocin inhibits urea-induced amyloid formation by bovine β-lactoglobulin

2021 ◽  
Vol 45 (5) ◽  
pp. 2589-2596
Author(s):  
Vijaya Lakshmi Bodiga ◽  
Madhukar Rao Kudle ◽  
Praveen Kumar Vemuri ◽  
Sreedhar Bodiga
Keyword(s):  
Amyloid Formation ◽  
Native Structure ◽  
Sheet Structure ◽  
Β Lactoglobulin ◽  
Β Sheet

Crocin stabilizes the native structure of β-lactoglobulin and attenuates urea-induced unfolding and loss of β-sheet structure during amyloidogenesis.

scholarly journals Theoretical Effect of Temperature on Threshold in the Hodgkin-Huxley Nerve Model

1966 ◽  
Vol 49 (5) ◽  
pp. 989-1005 ◽  
Author(s):  
Richard Fitzhugh
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Giant Axon ◽  
Temperature Curve ◽  
Effect Of Temperature ◽  
Threshold Temperature ◽  
Ionic Conductances ◽  
And Shifts ◽  
The Right ◽  
Increasing Temperature

In the squid giant axon, Sjodin and Mullins (1958), using 1 msec duration pulses, found a decrease of threshold with increasing temperature, while Guttman (1962), using 100 msec pulses, found an increase. Both results are qualitatively predicted by the Hodgkin-Huxley model. The threshold vs. temperature curve varies so much with the assumptions made regarding the temperature-dependence of the membrane ionic conductances that quantitative comparison between theory and experiment is not yet possible. For very short pulses, increasing temperature has two effects. (1) At lower temperatures the decrease of relaxation time of Na activation (m) relative to the electrical (RC) relaxation time favors excitation and decreases threshold. (2) For higher temperatures, effect (1) saturates, but the decreasing relaxation times of Na inactivation (h) and K activation (n) factor accommodation and increased threshold. The result is a U-shaped threshold temperature curve. R. Guttman has obtained such U-shaped curves for 50 µsec pulses. Assuming higher ionic conductances decreases the electrical relaxation time and shifts the curve to the right along the temperature axis. Making the conductances increase with temperature flattens the curve. Using very long pulses favors effect (2) over (1) and makes threshold increase monotonically with temperature.

On the roles of the alanine and serine in the β-sheet structure of fibroin

2015 ◽  
Vol 197 ◽  
pp. 10-17 ◽  
Author(s):  
Juan Francisco Carrascoza Mayen ◽  
Alexandru Lupan ◽  
Ciprian Cosar ◽  
Attila-Zsolt Kun ◽  
Radu Silaghi-Dumitrescu
Keyword(s):  
Sheet Structure ◽  
Β Sheet

Is folding of β-lactoglobulin non-hierarchic? intermediate with native-like β-sheet and non-native α-helix 1 1Edited by C. R. Matthews

2000 ◽  
Vol 296 (4) ◽  
pp. 1039-1051 ◽  
Author(s):  
Vincent Forge ◽  
Masaru Hoshino ◽  
Kazuo Kuwata ◽  
Munehito Arai ◽  
Kunihiro Kuwajima ◽  
...  
Keyword(s):  
Α Helix ◽  
Β Lactoglobulin ◽  
Β Sheet

scholarly journals A large area diamond-based beam tagging hodoscope for ion therapy monitoring

2018 ◽  
Vol 170 ◽  
pp. 09005 ◽  
Author(s):  
M.-L. Gallin-Martel ◽  
L. Abbassi ◽  
A. Bes ◽  
G. Bosson ◽  
J. Collot ◽  
...  
Keyword(s):  
Detection Efficiency ◽  
Signal To Noise Ratio ◽  
Therapy Monitoring ◽  
Chemical Vapor ◽  
X Rays ◽  
Reaction Products ◽  
Large Area ◽  
Position Measurement ◽  
Set Up ◽  
Good Signal

The MoniDiam project is part of the French national collaboration CLaRyS (Contrôle en Ligne de l’hAdronthérapie par RaYonnements Secondaires) for on-line monitoring of hadron therapy. It relies on the imaging of nuclear reaction products that is related to the ion range. The goal here is to provide large area beam detectors with a high detection efficiency for carbon or proton beams giving time and position measurement at 100 MHz count rates (beam tagging hodoscope). High radiation hardness and intrinsic electronic properties make diamonds reliable and very fast detectors with a good signal to noise ratio. Commercial Chemical Vapor Deposited (CVD) poly-crystalline, heteroepitaxial and monocrystalline diamonds were studied. Their applicability as a particle detector was investigated using α and β radioactive sources, 95 MeV/u carbon ion beams at GANIL and 8.5 keV X-ray photon bunches from ESRF. This facility offers the unique capability of providing a focused (~1 μm) beam in bunches of 100 ps duration, with an almost uniform energy deposition in the irradiated detector volume, therefore mimicking the interaction of single ions. A signal rise time resolution ranging from 20 to 90 ps rms and an energy resolution of 7 to 9% were measured using diamonds with aluminum disk shaped surface metallization. This enabled us to conclude that polycrystalline CVD diamond detectors are good candidates for our beam tagging hodoscope development. Recently, double-side stripped metallized diamonds were tested using the XBIC (X Rays Beam Induced Current) set-up of the ID21 beamline at ESRF which permits us to evaluate the capability of diamond to be used as position sensitive detector. The final detector will consist in a mosaic arrangement of double-side stripped diamond sensors read out by a dedicated fast-integrated electronics of several hundreds of channels.

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