Role of the orientation of -OH groups in the sensitivity and selectivity of the interaction of M(2+) with ribosyl- and galactosyl-imino-conjugates.
Three glyco-conjugates, viz., L(1), L(2) and L(3), which differ either in their carbohydrate moiety or in their aromatic moiety or both, were synthesized and characterized and were shown to have beta-anomeric form based on (1)H NMR and optical rotation studies. Metal ion interaction studies carried out in solution by emission and absorption spectral techniques exhibited selectivity towards Cu(2+) in HEPES buffer and a two fold higher sensitivity for L(2) as compared to L(1). The composition of the complexed species has been established based on ESI MS. Dinuclear-Cu(II) complexes of all these conjugates have been synthesized and characterized based on analytical and spectral methods including FTIR, (1)H NMR, FAB MS, EPR, ORD, CD and magnetism, and the structures of and have been established based on single crystal XRD. The structures revealed subtle differences present in the orientation of the -OH groups and also their ion binding preferences both at the molecular level as well as at the lattice levels. In the dinuclear-Cu(II) complexes, while C3-O(-) of ribosyl acts as a bridging moiety in , it is the C2-O(-) of galactosyl that bridges in and the Cu(2)O(2) cores are stabilized by two intra-complex H-bond interactions formed using C4-OH in the case of and C3-OH in the case of . While the glyco-moiety is poised perpendicular to the average plane of the Cu(2)O(2) core in , this is in plane in the case of 3.
Singhal
Nitin K
NK
Bioinorganic Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
Mitra
Atanu
A
Rajsekhar
Gudneppanaver
G
Shaikh
Mobin M
MM
Kumar
Subodh
S
Guionneau
Philippe
P
Rao
Chebrolu P
CP
D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D006001:Glycoconjugates / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D008670:Metals / Q000737:chemistry*; D008968:Molecular Conformation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
D006001:Glycoconjugates; D007097:Imines; D008670:Metals