疎水性コア、疎水コア

WordNet

remove the core or center from; "core an apple"
(computer science) a tiny ferrite toroid formerly used in a random access memory to store one bit of data; now superseded by semiconductor memories; "each core has three wires passing through it, providing the means to select and detect the contents of each bit" (同)magnetic core
a bar of magnetic material (as soft iron) that passes through a coil and serves to increase the inductance of the coil
the chamber of a nuclear reactor containing the fissile material where the reaction takes place
a small group of indispensable persons or things; "five periodicals make up the core of their publishing program" (同)nucleus, core group
a cylindrical sample of soil or rock obtained with a hollow drill
the center of an object; "the ball has a titanium core"
the central part of the Earth
lacking affinity for water; tending to repel and not absorb water; tending not to dissolve in or mix with or be wetted by water
abnormally afraid of water (同)aquaphobic

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〈C〉(果物の)『しん』 / 〈U〉(物事の)核心 / 〈C〉(電気の)磁心,磁極鉄心 / …‘の'しんを抜く
(驚いて)わあっ,えっ
Congress of Racial Equality(米国)人種平等会議

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/02/25 06:05:07」(JST)

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A droplet of water forms a spherical shape to minimize contact with the hydrophobic leaf.

The hydrophobic effect is the observed tendency of nonpolar substances to aggregate in aqueous solution and exclude water molecules.^[1]^[2] The name, literally meaning "water-fearing," describes the segregation and apparent repulsion between water and nonpolar substances. The hydrophobic effect explains the separation of a mixture of oil and water into its two components, and the beading of water on nonpolar surfaces such as waxy leaves. At the molecular level, the hydrophobic effect is important in driving protein folding,^[3]^[4] formation of lipid bilayers and micelles, insertion of membrane proteins into the nonpolar lipid environment and protein-small molecule interactions. Substances for which this effect is observed are known as hydrophobes.

Amphiphiles

Amphiphiles are molecules that have both hydrophobic and hydrophilic domains. Detergents are composed of amphiphiles that allow hydrophobic molecules to be solubilized in water by forming micelles and bilayers (as in soap bubbles). They are also important to cell membranes composed of amphiphilic phospholipids that prevent the internal aqueous environment of a cell from mixing with external water.

Folding of macromolecules

In the case of protein folding, the hydrophobic effect is important to understand the structure of proteins that have hydrophobic amino acids, such as alanine, valine, leucine, isoleucine, phenylalanine, tryptophan and methionine clustered together within the protein. Structures of water-soluble proteins have a hydrophobic core in which side chains are buried from water, which stabilizes the folded state, and charged and polar side chains are situated on the solvent-exposed surface where they interact with surrounding water molecules. Minimizing the number of hydrophobic side chains exposed to water is the principal driving force behind the folding process,^[5] although formation of hydrogen bonds within the protein also stabilizes protein structure.^[6]

The energetics of DNA tertiary structure assembly were determined to be driven by the hydrophobic effect, in addition to Watson-Crick base pairing (which is responsible for sequence selectivity) and a significant contribution from stacking interactions between the aromatic bases.^[7]^[8]

Protein purification

In biochemistry, the hydrophobic effect can be used to separate mixtures of proteins based on their hydrophobicity. Column chromatography with a hydrophobic stationary phase such as phenyl-sepharose will cause more hydrophobic proteins to travel more slowly, while less hydrophobic ones elute from the column sooner. To achieve better separation, a salt may be added (higher concentrations of salt increase the hydrophobic effect) and its concentration decreased as the separation goes on.

The origin of hydrophobic effect

See also: Entropic_force#Hydrophobic_force

Dynamic hydrogen bonds between molecules of liquid water

The hydrophobic interaction is mostly an entropic effect originating from the disruption of highly dynamic hydrogen bonds between molecules of liquid water by the nonpolar solute.^[9] A hydrocarbon chain or a similar nonpolar region or a big molecule is incapable of forming hydrogen bonds with water, introduction of such a non-hydrogen bonding surface into water causes disruption of the hydrogen bonding network between water molecules. The hydrogen bonds are reoriented tangential to such a surface to minimize disruption of the hydrogen bonded 3D network of water molecules and thus leads to a structured water "cage" around the nonpolar surface. The water molecules that form the "cage" (or solvation shell) have restricted mobilities. In the solvation shell of small nonpolar particles, the restriction amounts to some 10%, e.g. in the case of dissolved Xe at room temperature, a mobility restriction of 30% has been found.^[10] In the case of larger nonpolar molecules the reorientational and translational motion of the water molecules in the solvation shell may be restricted by a factor of two to four. Thus at 25°C the reorientational correlation time of water increases from 2 to 4-8 picoseconds. Generally, this leads to significant losses in translational and rotational entropy of water molecules and makes the process unfavorable in terms of free energy of the system.^[11] By aggregating together, nonpolar molecules reduce the surface area exposed to water and minimize their disruptive effect.

The hydrophobic effect can be quantified by measuring the partition coefficients of non-polar molecules between water and non-polar solvents. The partition coefficients can be transformed to free energy of transfer which includes enthalpic and entropic components, ΔG = ΔH - TΔS. These components are experimentally determined by calorimetry. The hydrophobic effect was found to be entropy-driven at room temperature because of the reduced mobility of water molecules in solvation shell of the non-polar solute. However, the enthalpic component of transfer energy was found to be favorable, meaning strengthening of water-water hydrogen bonds in the solvation shell, apparently due to the reduced mobility of water molecules. At the higher temperature, when water molecules became more mobile, this energy gain decreases, but so does the entropic component. As a result of such entropy-enthalpy compensation, the hydrophobic effect (as measured by the free energy of transfer) is only weakly temperature-dependent and became smaller at the lower temperature, which leads to "cold denaturation" of proteins.

References

^ Nic, M.; Jirat, J.; Kosata, B., eds. (2006–). "hydrophobic interaction". IUPAC Compendium of Chemical Terminology (Online ed.). doi:10.1351/goldbook.H02907. ISBN 0-9678550-9-8. http://goldbook.iupac.org/H02907.html.
^ Interfaces and the driving force of hydrophobic assembly Nature, Volume 437, Issue 7059, pp. 640-647 (2005)doi:10.1038/nature04162
^ Kauzmann W (1959). "Some factors in the interpretation of protein denaturation". Advances in Protein Chemistry 14: 1–63. doi:10.1016/S0065-3233(08)60608-7. PMID 14404936.
^ Charton, M.; Charton, B. I. (1982). "The structural dependence of amino acid hydrophobicity parameters". Journal of Theoretical Biology 99 (4): 629–644. doi:10.1016/0022-5193(82)90191-6. PMID 7183857. edit
^ Pace C, Shirley B, McNutt M, Gajiwala K (1 January 1996). "Forces contributing to the conformational stability of proteins". FASEB J. 10 (1): 75–83. PMID 8566551. http://www.fasebj.org/cgi/reprint/10/1/75.
^ Rose G, Fleming P, Banavar J, Maritan A (2006). "A backbone-based theory of protein folding". Proc. Natl. Acad. Sci. U.S.A. 103 (45): 16623–33. doi:10.1073/pnas.0606843103. PMC 1636505. PMID 17075053. http://www.pnas.org/cgi/content/abstract/103/45/16623.
^ Gilbert, H.F. (2000) Basic Concepts in Biochemistry - A Student's Survival Guide (2nd Edition). McGraw-Hill page 9.
^ van Holde K.E., Johnson W.C. and Ho P.S. Principles of Physical Biochemistry (Prentice-Hall 1998) page 18. See also thermodynamic discussion pages 137-144.
^ Silverstein, T. P. (1998). "The Real Reason Why Oil and Water Don't Mix". Journal of Chemical Education 75: 116–346. doi:10.1021/ed075p116. http://facstaff.unca.edu/jschmelt/oilwater.pdf. Retrieved 09 December 2011. edit
^ Haselmeier, R.; Holz, M.; Marbach, W.; Weingaertner, H. (1995). "Water Dynamics near a Dissolved Noble Gas. First Direct Experimental Evidence for a Retardation Effect". The Journal of Physical Chemistry 99 (8): 2243. doi:10.1021/j100008a001. edit
^ Charles Tanford (1973). The Hydrophobic Effect: Formation of Micelles and Biological Membranes. New York, NY: John Wiley & Sons Inc. ISBN 978-0-471-84460-0.

UpToDate Contents

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English Journal

Development of innovative oil-core self-organized nanovesicles prepared with chitosan and lecithin using a 2(3) full-factorial design.

Haas SE1, de Andrade C, Sansone PE, Guterres S, Dalla Costa T.
Pharmaceutical development and technology.Pharm Dev Technol.2014 Nov;19(7):769-78. doi: 10.3109/10837450.2013.829094. Epub 2013 Sep 2.
The aim of this study was to develop innovative nanosystems with isopropyl myristate as the oil core of self-assembly nanovesicles constituted of chitosan and lecithin using a 2(3) factorial design. The factors analyzed were chitosan (X1, levels 4 and 8 mg/ml), oil (X2, levels 10 and 20 mg/ml)
PMID 23998248

The fuzzy oil drop model, based on hydrophobicity density distribution, generalizes the influence of water environment on protein structure and function.

Banach M1, Konieczny L2, Roterman I3.
Journal of theoretical biology.J Theor Biol.2014 Oct 21;359:6-17. doi: 10.1016/j.jtbi.2014.05.007. Epub 2014 May 21.
In this paper we show that the fuzzy oil drop model represents a general framework for describing the generation of hydrophobic cores in proteins and thus provides insight into the influence of the water environment upon protein structure and stability. The model has been successfully applied in the
PMID 24859428

Binding of Aβ peptide creates lipid density depression in DMPC bilayer.

Lockhart C1, Klimov DK2.
Biochimica et biophysica acta.Biochim Biophys Acta.2014 Oct;1838(10):2678-88. doi: 10.1016/j.bbamem.2014.07.010. Epub 2014 Jul 15.
Using isobaric-isothermal replica exchange molecular dynamics and all-atom explicit water model we study the impact of Aβ monomer binding on the equilibrium properties of DMPC bilayer. We found that partial insertion of Aβ peptide into the bilayer reduces the density of lipids in the binding "foot
PMID 25037005

Japanese Journal

Crystal structure of peroxisomal targeting signal-2 bound to its receptor complex Pex7p–Pex21p

Pan Dongqing,Nakatsu Toru,Kato Hiroaki
Nature Structural & Molecular Biology, 2013-06-30
… The C-terminal region of Pex21p directly covers the hydrophobic surfaces of both Pex7p and PTS2, and the resulting hydrophobic core is the primary determinant of stable complex formation. …
NAID 120005296103

ヒトMAPキナーゼJNK1の立体構造・機能・安定性に対する遊離システイン残基の置換効果

仲庭哲津子,深田はるみ,黒木良太 [他],木下誉富
日本結晶学会誌 55(3), 197-202, 2013
… The surface cysteine involved in the molecular-surface hydrophobic pocket did not affect biological function; … Cysteines in the loosely-assembled hydrophobic environment moderately contributed to thermal stability and the mutations of these cysteines had negligible effect on enzyme activity. … The other cysteines are involved in the tightly-filled hydrophobic core and mutation of these residues conferred the adverse effects on the thermal stability and enzyme activity. …
NAID 130003373905

ヒト唾液短鎖ヒスタチンの口内炎菌（Candida albicans NBRC 1385株）の細胞膜に対する作動性

大滝俊樹,笠原仁,武井教展,谷口正之,加藤哲男,斎藤英一,Ohtaki Toshiki,Kasahara Hitoshi,Takei Norinobu,Taniguchi Masayuki,Kato Tetsuo,Saitoh Eiichi
新潟工科大学研究紀要 17, 29-34, 2012-12
… On the membrane surface, the histatins may not only form the pores by placing their hydrophobic part in contact with the hydrophobic core of membrane but also lead to the collapse of the membrane. …
NAID 120005207757