Platinum-coated, conductive atomic force microscope cantilevers were used to deposit electrophoretically purple membranes from Halobacterium salinarum on the bottom part of the cantilevers. By illuminating the bacteriorhodopsin-containing purple membranes, the protein goes through its photochemical reaction cycle, during which a conformational change happens in the protein, changing its shape and size. The size change of the protein acts upon the cantilever by causing its deflection, which can be monitored by the detection system of the atomic force microscope. The shape of the signal, the action spectrum of the deflection amplitude, and the blue light inhibition of the deflection all prove that the origin of the signal is the conformational change arising in the bacteriorhodopsin during the photocycle. From the size of the signal, the magnitude of the protein motion could be estimated. Using polarized light, the orientation of the motion was determined, relative to the transition moment of the retinal.

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The determination of the masses of supersymmetric particles, such as the selectron, for energies above threshold using the energy end-point method is subject to signal deconvolution difficulties and to standard model and supersymmetry backgrounds. The important features of ẽ R,L Ϯ production are used to design an experimentally robust method, with good resolution, both for determining the ẽ R,L and the 1 0 masses and for suppressing backgrounds. Additional features, such as the determination of the relative leptonic branching ratios of the selectron are present in the method. The determination of supersymmetric particle masses using the energy end-point method ͓1͔ is well known. The measurement of selectron masses is subject to two experimental difficulties: on the one hand, the energy distribution of the visible particles in the event is an overlap of 4 ''box like'' distributions due to the production channels ẽϪ and, on the other, the supersymmetry ͑SUSY͒ signal is masked by very large standard model ͑SM͒ backgrounds, such as W ϩ W Ϫ and ␥*␥*. The consequences are, for the former, the difficulty of resolving overlapping ''box'' edges in the lower energy region making it hard to determine which edge is due to which SUSY particle decay, while, for the latter, the masking of the SUSY signal by large SM backgrounds.Many other studies ͓2-6͔ of the determination of supersymmetric masses via the energy spectrum of the observed particles have been carried out showing the usefulness of the technique and the levels of accuracy possible. The complications in the selectron spectrum are being solved here.We realized that the difference of the observed positron and electron ͑from the ẽ L,R decay͒ energy distributions enhanced by the difference in cross sections with incident electron polarization ͑possible only with a linear collider͒ can solve these problems and provide a method by which we can determine the masses unambiguously with good resolution. In addition it offers new features, builtin redundancy, and the determination of the partial leptonic branching ratios to the channels 1 Ϯ e and 1 0 e. Information about the 1 Ϯ and 1 Ϯ masses may, in principle, also be determined. The e ϩ , e Ϫ energy distributions difference is given bywhere, for instance, LR is the production cross section for ẽ L ϩ ẽ R Ϫ , while RЈ(E) and LЈ(E) are the appropriate energy box distributions ͑for the incident electron right-handed and left-handed polarization͒ each normalized to unity. The method presented here removes the contribution to the energy spectrum from the reactions producing ẽ R ϩ ẽ R Ϫ and ẽ L ϩ ẽ L Ϫ , which solves the mass measurement difficulty and reduces the mass errors.Asymmetric boosts are present when ẽ L Ϯ and ẽ R Ϯ are produced in the same reaction. The values of the boosts being, in this case,The energies of the electron and positron which are the particles visible in the event are related to the decay c.m. energy. Since m e ӶM L,R we obtain the lower and higher bounds of the electron or positron energy distribution in ...

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