Isomorphic replacement label

Metal clusters have also been considered as heavy metal labels for determining the phasing in crystallography of large biological molecules.Heavy atom labeling by a tetrairidium cluster was used to determine the X-ray crystal structure of the small subunit from Thermus thermophilus. Attachment of the cluster was made to the surface-exposed SH groups prior to crystallization. The positions of these sulfhydryls were localized in difference Fourier maps that were constructed with the multiple isomorphous replacement (MIR). ... 

The Hiickel Hamiltonian-matrix for an n-annulene (Fig. 5-1) is the matrix in the determinant found in equation (5-1), with the quantities ( — x), along the diagonal, replaced by zero (i.e. a). As pointed out in Appendix A, this matrix is isomorphic with the adjacency matrix, A(C ), of the correspondingly-labelled molecular graph furthermore, the eigenvalues of the matrix, A(C ), are the annulene energy-levels we require (expressed in units of fi and... 

Recently, Shimizu s group reported enhanced proton conduction in a MOF by isomorphous ligand replacement. They modified the structure of a previously investigated MOF [Na3(2,4,6-trihydroxy-1,3,5-benzene-trisulfonate), labeled p-PCMOF-2] to host triazole molecules, as will be discussed in Section 3.3.2. ... 

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