Homonuclear small-size

Herein we describe the synthesis and characterization of small-size homonuclear gold cluster compounds with a nuclearity ranging from 3 to 39 gold atoms. These types of dusters are usually characterized through definitive structural techniques such as single-crystal X-ray diffraction, enabling in-depth study of the structural arrangements found in the solid state. 

Allowing only positive and rather significant electric field values permits the calculation of the dipole moment of the heteronuclear species. Applying the same approach to homonuclear species (H2, D2, and T2) should give the dipoles identically equal to zero. In our calculations, these actually come out to 10 . This small noise that entered our calculations was due in part to the previously mentioned fact that the zero-field wave function we use is not an eigenfunction of as it should be. The level of noise introduced is negligible, because 10 is four orders of magnitude smaller than the size of the dipole moments for the heteronuclear species. 

A protein subject to NMR analysis may have 100-200 amino acid residues, which provide a 1H NMR spectrum of many hundreds of lines. Because the amino acid sequence can be assumed to have been determined previously by non-NMR methods, the first step in the NMR study is to assign each line in the spectrum to a specific moiety (NH, ot-CH, side chain CH3, etc.) of a specific amino acid residue. Without the 2D methods that we have discussed, it would be virtually impossible to make such assignments. For relatively small proteins ( 50—100 residues) it is often possible to use conventional homonuclear 2D methods, such as COSY and HOHAHA, to define some bonding paths and to supplement these results with NOE data for residues that are very close in space as a result of secondary structural elements such as a helices. However, for proteins of moderate size such techniques are insufficient, and special methods had to be developed and now constitute the standard method of making sequential assignments. 

---