Lukins P B
School of Physics A28, University of Sydney, New South Wales, 2006,
Biochem Biophys Res Commun. 1999 Mar 16;256(2):288-92. doi: 10.1006/bbrc.1999.0330.
Electronic spectroscopy of a single biological molecule is demonstrated with approximately 4 A spatial resolution. The light-harvesting complex II (LHC II), in the ground and photo-excited states, was studied using scanning tunneling microscopy and spectroscopy of intact Photosystem II complexes. Analysis of the spectra indicates that the main mechanisms of tunneling between the STM tip and the surface involve delocalized electronic states of the LHC II and local vibronic states associated with C=C, C=O, C-H, N-H, and O-H groups near the LHC II surface. Conduction within the bulk LHC II is then due to ohmic and hopping conduction as well as tunneling between amino acid residues. Light activation of LHC II occurs via a photoconductive rather than a photovoltaic mechanism. There is a dramatic light-induced increase in the electronic density of states indicating a light-induced enhancement of energy and electron delocalization which is important for the efficient and rapid transfer of excitation energy from LHC II to the Photosystem II reaction center.
以约4埃的空间分辨率展示了单个生物分子的电子光谱。利用扫描隧道显微镜和完整光系统II复合物的光谱，研究了处于基态和光激发态的捕光复合物II（LHC II）。光谱分析表明，STM针尖与表面之间的隧穿主要机制涉及LHC II的离域电子态以及与LHC II表面附近的C = C、C = O、C - H、N - H和O - H基团相关的局域振动电子态。然后，大块LHC II内的传导是由于欧姆传导和跳跃传导以及氨基酸残基之间的隧穿。LHC II的光激活是通过光电导机制而非光伏机制发生的。态密度存在显著的光致增加，表明光致增强了能量和电子离域，这对于激发能从LHC II高效快速转移到光系统II反应中心很重要。
