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Volumn 50, Issue 1, 2011, Pages 285-290

Light-driven transport of a molecular walker in either direction along a molecular track

Author keywords

Brownian ratchets; dynamic covalent chemistry; molecular devices; molecular motors; photochemistry

Indexed keywords

BROWNIAN MOVEMENT; PHOTOCHEMICAL REACTIONS;

EID: 78650707512     PISSN: 14337851     EISSN: 15213773     Source Type: Journal    
DOI: 10.1002/anie.201004779     Document Type: Article
Times cited : (138)

References (81)
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    • For concise reviews on motor proteins, see: kinesin family
    • For concise reviews on motor proteins, see: kinesin family
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    • We use the term "ratcheting" in a manner that is consistent with its use in biology and nonequilibrium statistical physics: namely, it is the capturing of a positional displacement of a substrate through the imposition of a kinetic energy barrier that prevents the displacement being reversed when the thermodynamic driving force is removed; see,. An information ratchet is a Brownian ratchet mechanism in which the position of the particle on a potential energy surface causes the potential energy surface to change (at an energetic cost), thus leading to directional transport of the particle. In an energy ratchet mechanism the potential energy surface is periodically or stochastically varied irrespective of the position of the particle in order to cause directional transport (for example, the relative depths of two pairs of minima and the relative heights of the maxima that connect them could be repeatedly switched, as in Figure 1 b). See ref. [10a].
    • We use the term "ratcheting" in a manner that is consistent with its use in biology and nonequilibrium statistical physics: namely, it is the capturing of a positional displacement of a substrate through the imposition of a kinetic energy barrier that prevents the displacement being reversed when the thermodynamic driving force is removed; see, M. N. Chatterjee, E. R. Kay, D. A. Leigh, J. Am. Chem. Soc. 2006, 128, 4058-4073. An information ratchet is a Brownian ratchet mechanism in which the position of the particle on a potential energy surface causes the potential energy surface to change (at an energetic cost), thus leading to directional transport of the particle. In an energy ratchet mechanism the potential energy surface is periodically or stochastically varied irrespective of the position of the particle in order to cause directional transport (for example, the relative depths of two pairs of minima and the relative heights of the maxima that connect them could be repeatedly switched, as in Figure 1 b). See ref. [10a].
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    • Chatterjee, M.N.1    Kay, E.R.2    Leigh, D.A.3
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    • For examples of light-driven synthetic molecular machines, see
    • For examples of light-driven synthetic molecular machines, see
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    • For elegant mechanistic studies based on ring strain in macrocycles that contain a "stiff stilbene" linkage, see
    • For elegant mechanistic studies based on ring strain in macrocycles that contain a "stiff stilbene" linkage, see
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    • For a dynamic covalent library that consists of macrocycles with internal acyl hydrazone and (photoswitchable) azobenzene linkages, see
    • Angew. Chem. Int. Ed. 2009, 48, 7040-7043. For a dynamic covalent library that consists of macrocycles with internal acyl hydrazone and (photoswitchable) azobenzene linkages, see
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    • note
    • The 1,4 isomers of 1, which result from folding of the track (see the Supporting Information for structures), add an additional double-step mechanism to the major passing-leg gait mechanism (see ref. [4]). This pathway has the opposite bias to the main mechanism and so actually reduces the net directionality of the walker transport.
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    • E or Z denotes the configuration of the stilbene double bond in the track; the numerical prefixes (e.g., 1,2) specify the position of the walker unit on the four-foothold track.
    • E or Z denotes the configuration of the stilbene double bond in the track; the numerical prefixes (e.g., 1,2) specify the position of the walker unit on the four-foothold track.
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    • The sulfur foothold of the track was protected as a disulfide with a "placeholder" thiol in order to prevent oxidation of the free thiol to a dimeric disulfide by atmospheric oxygen.
    • The sulfur foothold of the track was protected as a disulfide with a "placeholder" thiol in order to prevent oxidation of the free thiol to a dimeric disulfide by atmospheric oxygen.
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    • The styrene (Type II) olefins in 7 and 8 have similar reactivities and so the maximum yield of E-1,2- 1 expected from their statistical cross-metathesis is 50 % (see ref. [14a]). This synthetic disconnection was chosen to prevent scrambling of the sensitive (different) disulfide and aldehyde/hydrazone functionalities in the final molecule.
    • The styrene (Type II) olefins in 7 and 8 have similar reactivities and so the maximum yield of E-1,2- 1 expected from their statistical cross-metathesis is 50 % (see ref. [14a]). This synthetic disconnection was chosen to prevent scrambling of the sensitive (different) disulfide and aldehyde/hydrazone functionalities in the final molecule.
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    • For an excellent review on the photochemistry of stilbene derivatives, see
    • For an excellent review on the photochemistry of stilbene derivatives, see:, H. Meier, Angew. Chem. 1992, 104, 1425-1446
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    • note
    • Z), the quantum yield ratio is usually approximately 1 (see ref. [17]).
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    • . radicals (here photogenerated with green light) to the double bond. See, for example.
    • . radicals (here photogenerated with green light) to the double bond. See, for example:, S. Yamashita, Bull. Chem. Soc. Jpn. 1961, 34, 972-976.
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    • The iodine-mediated stilbene Z→E isomerization reactions were conducted at relatively low concentrations (0.1 m M) of the walker-track conjugate and with a narrow (10 nm) bandwidth of green light (500 nm) to avoid side-reactions of the disulfide groups.
    • The iodine-mediated stilbene Z→E isomerization reactions were conducted at relatively low concentrations (0.1 m M) of the walker-track conjugate and with a narrow (10 nm) bandwidth of green light (500 nm) to avoid side-reactions of the disulfide groups.
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    • 78650713253 scopus 로고    scopus 로고
    • The length of the methylene spacer in the walker unit is crucial in order to generate ring strain in E-2,3- 1, but not in Z-2,3- 1. The choice of a four-carbon atom spacer was based on model studies and molecular modeling (semi-empirical, PM3).
    • The length of the methylene spacer in the walker unit is crucial in order to generate ring strain in E-2,3- 1, but not in Z-2,3- 1. The choice of a four-carbon atom spacer was based on model studies and molecular modeling (semi-empirical, PM3).
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    • For studies on the dynamic chemistry of hydrazone-disulfide systems under mutually exclusive (acid-base) conditions, see
    • For studies on the dynamic chemistry of hydrazone-disulfide systems under mutually exclusive (acid-base) conditions, see
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    • 1H NMR integration.
    • 1H NMR integration.
  • 80
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    • The presence of the walker at the 2,3-position lowers the E/Z ratio at the photostationary state of the Z→E reaction (Scheme 2 b), thus reducing the net directionality of the transport mechanism.
    • The presence of the walker at the 2,3-position lowers the E/Z ratio at the photostationary state of the Z→E reaction (Scheme 2 b), thus reducing the net directionality of the transport mechanism.
  • 81
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    • In a double-labeling crossover experiment on the previously reported small-molecule walker-track system (see ref. [4]), an average step number (the number of steps after which 50 % of the walkers are no longer attached to their original track) of 37 was obtained for the loss of processivity during disulfide and hydrazone exchange. The conditions for dynamic covalent bond exchange are the same in the present study, and walker dissociation is not observed during the photochemical experiments. Therefore, the average step number during the operation of 1 should be similar. The average step number for wild-type kinesin is approximately 100 ().
    • In a double-labeling crossover experiment on the previously reported small-molecule walker-track system (see ref. [4]), an average step number (the number of steps after which 50 % of the walkers are no longer attached to their original track) of 37 was obtained for the loss of processivity during disulfide and hydrazone exchange. The conditions for dynamic covalent bond exchange are the same in the present study, and walker dissociation is not observed during the photochemical experiments. Therefore, the average step number during the operation of 1 should be similar. The average step number for wild-type kinesin is approximately 100 (, R. B. Case, D. W. Pierce, N. Hom-Booher, C. L. Hart, R. D. Vale, Cell 1997, 90, 959-966).
    • (1997) Cell , vol.90 , pp. 959-966
    • Case, R.B.1    Pierce, D.W.2    Hom-Booher, N.3    Hart, C.L.4    Vale, R.D.5


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.