Thermal proteins

Eggers, D.K. and Valentine, J.S. (2001) Molecular confinement influences protein structure and enhances thermal protein stability. Protein Science, 10, 250-261. 

Figure 8 Illustration of the flash-quench technique for measuring intramolecular ET rates. Photoexcitation of Ru(II)(bpy)2(imidazole)(amine)2+, Ru(II)(bpy), bound to ferro-cytochrome c, Fe(II)P, produced an 80-ns lived metal-to-ligand charge transfer (MLCT) excited state, Ru(III)(bpy -), which was oxidatively quenched by bimolecular reaction with Ru(NH3) +. The resulting Ru(III)-complex was then reduced by the Fe(II)P through thermal, protein-mediated ET. Finally bimolecular reaction of the Ru(II)/Fe(III)P product with Ru(NH3) + re-formed the starting Ru(II)-protein-Fe(II)P complex.

The rotational dynamics on the protein surface is basically shaped by electrostatic interactions alone and the HBs formed by water with the protein surface break the quasi-isotropic nature of the dipolar rotation that is found in the bulk. Also, for the fiilly thermalized protein, a ratio between the characteristic times of the first and the second dipole-dipole correlation function, yff = /r, of about 5 is at variance... 

In addition, protein motion reduces the retardation of the water dynamics, because the dimension of the water translational space is increased and at the same time the decay of the orientational correlation is accelerated. In spite of this accelerated dynamics, hydration water diffusion remains anomalous for a thermalized protein. 

ABSTRACT Electrical phenomena in artificial cells are described. The constituent material of the cells, referred to as proteinoid or as thermal protein, have been extensively studied in the context of the origin of life, which led to the finding of excitability as one of the biofunctions. The activities found in proteinoid cells are such as to make them useful models for modern excitable cells as well as for protocells. For example, the proteinoid cells display double membrane, asymmetric permeability, membrane potentials, action potentials, and photoactivity. 

The proteinoids, thermal copolyamino acids, represent a spectrum of polymers having compositions and structures like those of natural proteins and peptides. Since they are products of the synthetic laboratory, compositions not known in nature may be produced in abundance, and in sensitively graded products. These materials are referred to as artificial proteins, synthetic proteins, thermal proteins, or proteinoids. The last term is used because of the similarity to proteins. Since 1972, each semiannual... 

The only up-to-date suitable experimental model to help answer this question is the proteinoid cell assembled from thermal proteins, or proteinoids. To date, no other experimental protein-related model of the first cell has been shown to have comparable properties. 

Fig. 3. Differential scanning calorimetry scans of biomembrane transitions, all obtained with 50% ethylene glycol/water as solvent. (A) A. laidlawii membranes from cells grown in tryptose medium at 37 C (B) lysodeikticus membranes from cells grown in brain heart infusion at 37 C (C) JE. coli K12W945 whole cells grown in minimal salts with glucose at 20 C (D) the same cells as in (C), but scanned after thermal protein (E) rat liver microsomes (F) rat liver In all cases a lower temperature reversible lipid transition is followed by a higher temperature irreversible protein peak. The protein denaturation peaks are featureless in (A), (E), and (F), but show fine structure in (B), (C), and (D). Unlike other organisms, coli after heating shows two lipid transitions and residual reversible protein denaturation, as seen in (D).

Shrake, A. Ross, P.D. (1992) Origin and consequences of Hgand-induced multiphasic thermal protein denaturation. Biopolymers, Vol. 32, pp. 925-940. 

The interest in vesicles as models for cell biomembranes has led to much work on the interactions within and between lipid layers. The primary contributions to vesicle stability and curvature include those familiar to us already, the electrostatic interactions between charged head groups (Chapter V) and the van der Waals interaction between layers (Chapter VI). An additional force due to thermal fluctuations in membranes produces a steric repulsion between membranes known as the Helfrich or undulation interaction. This force has been quantified by Sackmann and co-workers using reflection interference contrast microscopy to monitor vesicles weakly adhering to a solid substrate [78]. Membrane fluctuation forces may influence the interactions between proteins embedded in them [79]. Finally, in balance with these forces, bending elasticity helps determine shape transitions [80], interactions between inclusions [81], aggregation of membrane junctions [82], and unbinding of pinched membranes [83]. Specific interactions between membrane embedded receptors add an additional complication to biomembrane behavior. These have been stud-... 

Steadman B L, Thompson K C, MIddaugh C R, Matsuno K, Vrona S, Lawson E Q and Lewis R V 1992 The effects of surface adsorption on the thermal stability of proteins Bioteoh. Bioengng. 40 8-15... 

Most potential energy surfaces are extremely complex. Fiber and Karplus analyzed a 300 psec molecular dynamics trajectory of the protein myoglobin. They estimate that 2000 thermally accessible minima exist near the native protein structure. The total number of conformations is even larger. Dill derived a formula to calculate the upper bound of thermally accessible conformations in a protein. Using this formula, a protein of 150 residues (the approx-... 

Evaporation from a spray of charged droplets produced from a stream of liquid yields ions that can be analyzed in a mass spectrometer. Thermally labile and normally nonvolatile substances such as sugars, peptides, and proteins can be examined successfully. 

The FAB source operates near room temperature, and ions of the substance of interest are lifted out from the matrix by a momentum-transfer process that deposits little excess of vibrational and rotational energy in the resulting quasi-molecular ion. Thus, a further advantage of FAB/LSIMS over many other methods of ionization lies in its gentle or mild treatment of thermally labile substances such as peptides, proteins, nucleosides, sugars, and so on, which can be ionized without degrading their. structures. 

As a rule of thumb, one can say that the efficiency of separation of mixtures and the simplicity of operating and maintaining apparatus are much greater for GC than for LC. Hence, other things being equal, GC is most often the technique of first choice and can be used with a very wide variety of compound types. However, for nonvolatile or thermally labile substances like peptides, proteins, nucleotides, sugars, carbohydrates, and many organometallics, GC may be ruled out completely... 

The ablated vapors constitute an aerosol that can be examined using a secondary ionization source. Thus, passing the aerosol into a plasma torch provides an excellent means of ionization, and by such methods isotope patterns or ratios are readily measurable from otherwise intractable materials such as bone or ceramics. If the sample examined is dissolved as a solid solution in a matrix, the rapid expansion of the matrix, often an organic acid, covolatilizes the entrained sample. Proton transfer from the matrix occurs to give protonated molecular ions of the sample. Normally thermally unstable, polar biomolecules such as proteins give good yields of protonated ions. This is the basis of matrix-assisted laser desorption ionization (MALDI). 

Folded proteins can be caused to spontaneously unfold upon being exposed to chaotropic agents, such as urea or guanidine hydrochloride (Gdn), or to elevated temperature (thermal denaturation). As solution conditions are changed by addition of denaturant, the mole fraction of denatured protein increases from a minimum of zero to a maximum of 1.0 in a characteristic unfolding isotherm (Fig. 7a). From a plot such as Figure 7a one can determine the concentration of denaturant, or the temperature in the case of thermal denaturation, required to achieve half maximal unfolding, ie, where... 

Disulfides. The introduction of disulfide bonds can have various effects on protein stability. In T4 lyso2yme, for example, the incorporation of some disulfides increases thermal stability others reduce stability (47—49). Stabili2ation is thought to result from reduction of the conformational entropy of the unfolded state, whereas in most cases the cause of destabili2ation is the introduction of dihedral angle stress. In natural proteins, placement of a disulfide bond at most positions within the polypeptide chain would result in unacceptable constraint of the a-carbon chain. 

Process Va.ria.tlons. The conventional techniques for tea manufacture have been replaced in part by newer processing methods adopted for a greater degree of automation and control. These newer methods include withering modification (78), different types of maceration equipment (79), closed systems for fermentation (80), and fluid-bed dryers (81). A thermal process has been described which utilizes decreased time periods for enzymatic reactions but depends on heat treatment at 50—65°C to develop black tea character (82). It is claimed that tannin—protein complex formation is decreased and, therefore, greater tannin extractabiUty is achieved. Tea value is beheved to be increased through use of this process. 

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