scholarly journals THE THERMAL STABILITY OF RHODOPSIN AND OPSIN

1958 ◽  
Vol 42 (2) ◽  
pp. 259-280 ◽  
Author(s):  
Ruth Hubbard
Keyword(s):  
Thermal Stability ◽  
Thermal Denaturation ◽  
Species Differences ◽  
Activation Energies ◽  
Specific Relationship ◽  
Thermal Bleaching ◽  
Thermal Stability Of ◽  
Cis Isomer

Rhodopsin, the red photosensitive pigment of rod vision, is composed of a specific cis isomer of retinene, neo-b (11-cis), joined as chromophore to a colorless protein, opsin. We have investigated the thermal denaturation of cattle rhodopsin and opsin in aqueous digitonin solution, and in isolated rod outer limbs. Both rhodopsin and opsin are more stable in rods than in solution. In solution as well as in rods, moreover, rhodopsin is considerably more stable than opsin. The chromophore therefore protects opsin against denaturation. This is true whether rhodopsin is extracted from dark-adapted retinas, or synthesized in vitro from neo-b retinene and opsin. Excess neo-b retinene does not protect rhodopsin against denaturation. The protection involves the specific relationship between the chromophore and opsin. Similar, though somewhat less, protection is afforded opsin by the stereoisomeric iso-a (9-cis) chromophore in isorhodopsin. The Arrhenius activation energies (Ea) and entropies of activation (ΔS‡) are much greater for thermal denaturation of rhodopsin and isorhodopsin than of opsin. Furthermore, these values differ considerably for rhodopsins from different species —frog, squid, cattle—presumably due to species differences in the opsins. Heat or light bleaches rhodopsin by different mechanisms, yielding different products. Light stereoisomerizes the retinene chromophore; heat denatures the opsin. Photochemical bleaching therefore yields all-trans retinene and native opsin; thermal bleaching, neo-b retinene and denatured opsin.

Effect of osmolytes on the thermal stability of proteins: replica exchange simulations of Trp-cage in urea and betaine solutions

2018 ◽  
Vol 20 (16) ◽  
pp. 11174-11182 ◽  
Author(s):  
Beata Adamczak ◽  
Mateusz Kogut ◽  
Jacek Czub
Keyword(s):  
Thermal Stability ◽  
Molecular Mechanism ◽  
Thermal Denaturation ◽  
Replica Exchange ◽  
Thermal Stability Of ◽  
Denaturation Of Proteins

Although osmolytes are known to modulate the folding equilibrium, the molecular mechanism of their effect on thermal denaturation of proteins is still poorly understood.

In silico and in vitro Approaches to Elucidate the Thermal Stability of Human UDP-glucuronosyltransferase (UGT) 1A9

2009 ◽  
Vol 24 (3) ◽  
pp. 235-244 ◽  
Author(s):  
Ryoichi Fujiwara ◽  
Miki Nakajima ◽  
Tetsunori Yamamoto ◽  
Hidemi Nagao ◽  
Tsuyoshi Yokoi
Keyword(s):  
Thermal Stability ◽  
In Silico ◽  
Udp Glucuronosyltransferase ◽  
Thermal Stability Of

Effects of glycine betaine and glycerophosphocholine on thermal stability of ribonuclease

1998 ◽  
Vol 274 (4) ◽  
pp. F762-F765 ◽  
Author(s):  
Maurice B. Burg ◽  
Eugenia M. Peters
Keyword(s):  
Thermal Stability ◽  
Tissue Culture ◽  
Glycine Betaine ◽  
Metabolic Cost ◽  
Rnase A ◽  
Renal Cells ◽  
And Function ◽  
Thermal Stability Of

Urea in renal medullas is sufficiently high to perturb macromolecules, yet the cells survive and function. The counteracting osmolytes hypothesis holds that methylamines, such as glycine betaine (betaine) and glycerophosphocholine (GPC) in renal medullas, stabilize macromolecules and oppose the effects of urea. Although betaine counteracts effects of urea on macromolecules in vitro and protects renal cells from urea in tissue culture, renal cells accumulate GPC rather than betaine in response to high urea both in vivo and in tissue culture. A proposed explanation is that GPC counteracts urea more effectively than betaine. However, we previously found GPC slightly less effective than betaine in counteracting inhibition of pyruvate kinase activity by urea. To test another macromolecule, we now compare GPC and betaine in counteracting reduction of the thermal stability of RNase A by urea. We find that urea decreases the thermal transition temperature and that betaine and GPC increase it, counteracting urea approximately equally. Therefore, the preference for GPC in response to high urea presumably has some other basis, such as a lower metabolic cost of GPC accumulation.

Synthesis and investigation of in vitro cytotoxic activities and thermal stability of novel pyridine derivative platinum (II) complexes vis a vis DFT studies

Polyhedron ◽  
2021 ◽  
pp. 115492
Author(s):  
Emine Kutlu ◽  
Fatih Mehmet Emen ◽  
Görkem Kismali ◽  
Neslihan Kaya Kınaytürk ◽  
Ali Ihsan Karacolak ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Pyridine Derivative ◽  
Cytotoxic Activities ◽  
Dft Studies ◽  
Thermal Stability Of

Thermal Stability of Cotton Cellulose Modified with Calcium Complexes

2014 ◽  
Vol 983 ◽  
pp. 218-221
Author(s):  
Ying Juan Sun ◽  
Yong Li Yang ◽  
Ming Gao
Keyword(s):  
Experimental Data ◽  
Thermal Stability ◽  
Thermal Decomposition ◽  
Thermal Degradation ◽  
Metal Ions ◽  
Activation Energies ◽  
Cone Calorimetry ◽  
Second Stage ◽  
Calcium Complexes ◽  
Thermal Stability Of

Complexes of cell-THPC-thiourea-ADP with Ca2+ have been prepared. The thermal stability and smoke suspension of the samples are determined by TG, DTA and cone calorimetry. The activation energies for the second stage of thermal degradation have been obtained by following Broido equation. Experimental data show that for the complexes of cell-THPC-thiourea-ADP with Ca2+, the activation energies and thermal decomposition temperatures are higher than those of cell-THPC-thiourea-ADP, which shows these metal ions can increase the thermal stability of cell-THPC-thiourea-ADP

scholarly journals Application of Glycation in Regulating the Heat-Induced Nanoparticles of Egg White Protein

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 943 ◽  
Author(s):  
Chenying Wang ◽  
Xidong Ren ◽  
Yujie Su ◽  
Yanjun Yang
Keyword(s):  
Thermal Stability ◽  
Protein Concentration ◽  
Thermal Denaturation ◽  
Negative Charge ◽  
Activity Index ◽  
Stability Index ◽  
Egg White ◽  
Egg White Protein ◽  
Neutral Conditions ◽  
Thermal Stability Of

Due to the poor thermal stability of egg white protein (EWP), important challenges remain regarding preparation of nanoparticles for EWP above the denaturation temperature at neutral conditions. In this study, nanoparticles were fabricated from conjugates of EWP and isomalto-oligosaccharide (IMO) after heating at 90 °C for 30 min. Meanwhile, the effects of protein concentration, temperature, pH, ionic strength and degree of glycation (DG) on the formation of nanoparticles from IMO-EWP were investigated. To further reveal the formation mechanism of the nanoparticles, structures, thermal denaturation properties and surface properties were compared between EWP and IMO-EWP conjugates. Furthermore, the emulsifying activity index (EAI) and the emulsifying stability index (ESI) of nanoparticles were determined. The results indicated that glycation enhanced thermal stability and net surface charge of EWP due to changes in the EWP structure. The thermal aggregation of EWP was inhibited significantly by glycation, and enhanced with a higher degree of glycation. Meanwhile, the nanoparticles (<200 nm in size) were obtained at pH 3.0, 7.0 and 9.0 in the presence of NaCl. The increased thermal stability and surface net negative charge after glycation contributed to the inhibition. The EAI and ESI of nanoparticles were increased nearly 3-fold and 2-fold respectively, as compared to unheated EWP.

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