The ability to tune the light‐absorption properties of chlorophylls by their protein environment is the key to the robustness and high efficiency of photosynthetic light‐harvesting proteins. Unfortunately, the intricacy of the natural complexes makes it very difficult to identify and isolate specific protein–pigment interactions that underlie the spectral‐tuning mechanisms. Herein we identify and demonstrate the tuning mechanism of chlorophyll spectra in type II water‐soluble chlorophyll binding proteins from Brassicaceae (WSCPs). By comparing the molecular structures of two natural WSCPs we correlate a shift in the chlorophyll red absorption band with deformation of its tetrapyrrole macrocycle that is induced by changing the position of a nearby tryptophan residue. We show by a set of reciprocal point mutations that this change accounts for up to 2/3 of the observed spectral shift between the two natural variants. 相似文献
A synchrotron microprobe has been used to characterize ion implantations of nickel and cobalt in silicon (100) or (111) wafers. The synchrotron radiation is collimated by means of a rigid cylindrical glass capillary of 110 mm length, 5 mm outer and 30 μm or 10 μm inner diameter. The beam is pointed at the wafer sample and the emitted radiation of X-rays is detected by an energy dispersive spectrometer. Line scans are recorded step by step over the implantation areas and across their borders. The sharpness of the borders is characterized at a lateral resolution of 13 μm and the edge lengths ranging from 0.6 to 8 mm are determined with an accuracy better than ± 20 μm. The signal intensity and implantation dose of cobalt ranging from 1 × 1015 to 1 × 1017 ions cm−2 show a linear relationship as is to be expected for the micrometre thin implanted layers. 相似文献
We consider solutions of a system of refinement equations written in the form
where the vector of functions is in and is a finitely supported sequence of matrices called the refinement mask. Associated with the mask is a linear operator defined on by . This paper is concerned with the convergence of the subdivision scheme associated with , i.e., the convergence of the sequence in the -norm.
Our main result characterizes the convergence of a subdivision scheme associated with the mask in terms of the joint spectral radius of two finite matrices derived from the mask. Along the way, properties of the joint spectral radius and its relation to the subdivision scheme are discussed. In particular, the -convergence of the subdivision scheme is characterized in terms of the spectral radius of the transition operator restricted to a certain invariant subspace. We analyze convergence of the subdivision scheme explicitly for several interesting classes of vector refinement equations.
Finally, the theory of vector subdivision schemes is used to characterize orthonormality of multiple refinable functions. This leads us to construct a class of continuous orthogonal double wavelets with symmetry.