Detergents membrane proteins

Solubilize desaturases with 1 % CHAPS at a detergent-membrane protein ratio of equal to one, 5°C for 30 min with gentle stirring. 

Aqueous-detergent solutions of appropriate concentration and temperature can phase separate to form two phases, one rich in detergents, possibly in the form of micelles, and the other depleted of the detergent (Piyde and Phillips, op. cit.). Proteins distribute between the two phases, hydrophobic (e.g., membrane) proteins reporting to the detergent-rich phase and hydrophilic proteins to the detergent-free phase. Indications are that the size-exclusion properties of these systems can also be exploited for viral separations. These systems would be handled in the same way as the aqueous two-phase systems. 

B30 611 1976 gave m 69-70°). Hydrolysis using an equivalent of base in methanol gave the desired glueoside. This is a non-ionie detergent for reeonstituting membrane proteins and has a critieal micelle concentration of 30 mM. [Shimamoto et al. J Biochem (Tokyo) 97 1807 I985 Saito and Tsuchiya Chem Pharm Bull Jpn 33... 

Figure 12.2 (a) Schematic drawing of membrane proteins in a typical membrane and their solubilization by detergents. The hydrophilic surfaces of the membrane proteins are indicated by red. (b) A membrane protein crystallized with detergents bound to its hydrophobic protein surface. The hydrophilic surfaces of the proteins and the symbols for detergents are as in (a). (Adapted from H. Michel, Trends Biochem. Sci. 8 56-59, 1983.)... 

Scientists initially approached structure-function relationships in proteins by separating them into classes based upon properties such as solubility, shape, or the presence of nonprotein groups. For example, the proteins that can be extracted from cells using solutions at physiologic pH and ionic strength are classified as soluble. Extraction of integral membrane proteins requires dissolution of the membrane with detergents. 

In the case of PS II membrane proteins, as discussed above, the hydrophobic and hydrophilic pairs of attached lipids can partially support the protein complex at the air-water interface, despite their large size and density. However, in the case of PS II core complex, the detergent strips the attached lipids and some extrinsic proteins. The remaining protein complex is water soluble. It is very difficult to prepare a stable monolayer of water-soluble proteins with the Langmuir method. Indeed, it is hard to directly prepare a stable monolayer of PS II core complex because of its water solubility as well as density. One possible solution is to change the density and ionic strength of the subphase [9]. 

Chevallet, M. Santoni, V. Poinas, A. Rouquie, D. Fuchs, A. Kieffer, S. Rossignol, M. Lunardi, J. Garin, J. Rabilloud, T. New zwitterionic detergents improve the analysis of membrane proteins by two-dimensional electrophoresis. Electrophoresis 1998,19,1901-1909. 

It is emphasized that revealing the dynamics as well as the structure (or conformation) based on several types of spin-relaxation times is undoubtedly a unique and indispensable means, only available from NMR techniques at ambient temperature of physiological significance. Usually, the structure data themselves are available also from X-ray diffraction studies in a more refined manner. Indeed, better structural data can be obtained at lower temperature by preventing the unnecessary molecular fluctuations, which are major subjects in this chapter, since structural data can be seriously deteriorated for domains where dynamics are predominant even in the 2D or 3D crystalline state or proteoliposome at ambient temperature. It should be also taken into account that the solubilization of membrane proteins in detergents is an alternative means to study structure in solution NMR. However, it is not always able faithfully to mimick the biomembrane environment, because the interface structure is not always the same between the bilayer and detergent system. This typically occurs in the case of PLC-81(1-140) described in Section 4.2.4 and other types of peptide systems. 

Fernandez C, Wuthrich K (2003) NMR solution structure determination of membrane proteins reconstituted in detergent micelles. FEBS Lett 555 144-150... 

Proteins that can be removed from membranes by washing them with salt solutions or low pH solutions (disrupts ionic interactions) are called peripheral membrane proteins. Proteins that cannot be removed without disrupting the membrane with detergents are called integral... 

APS represent an attractive novel way of stabilizing membrane proteins under conditions where they can be exposed to detergent-free media. In the present work, we report some preliminary experiments aimed at complexing with APS a photosynthetic PS2 reaction center core complex, that from the thermophilic cyanobacterium Thermosynechococcus elongatus. 

M. le Maire, P. Champed, J. V. Moller (2000) Interaction of membrane proteins and lipids with solubilizing detergents. Biochim. Biophys. Acta, 1508 86-111... 

C. Prata, F. Giusti, Y. Gohon, B. Pucci, J.-L. Popot, C. Tribet (2001) Non-ionic amphiphilic polymers derived from Tris(hydroxymethyl)-acrylamidomethane keep membrane proteins soluble and native in the absence of detergent. Biopolymers, 56 77-84... 

Photosystem I is a membrane pigment-protein complex in green plants, algae as well as cyanobacteria, and undergoes redox reactions by using the electrons transferred from photosystem II (PS II) [1], These membrane proteins are considered to be especially interesting in the study of monomolecular assemblies, because their structure contains hydrophilic area that can interact with the subphase as well as hydrophobic domains that can interact either with each other or with detergent and lipids [2], Moreover, studies with such proteins directly at the air-water interface are expected to be a valuable approach for their two-dimensional crystallization. 

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