A simple copper(II) complex of the anthracenylappended terpyridine ligand 4′-(anthracen-9-yl)-2,2′:6′,2′′-terpyridine (L), [Cu(L)Cl 2 ] (1, ESI-MS, m/z = 507.08), is reported as a highly selective "turn-on" optical imaging probe for L-cysteine. Probe 1 shows a Cu II /Cu I redox potential [E 1/2 = -0.194 V versus normal hydrogen electrode (NHE)] within a biologically viable range. The copper center in 1 adopts a square-pyramidal geometry (τ = 0.0851), and the Cu-N py bond (1.970 Å) of the middle pyridine (py) ring is shorter than the other two Cu-N py bonds (2.069 and 2.040 Å). The Cu-Cl bonds (2.444 and 2.027 Å) are labile enough to be replaced by solvent molecules. The squarebased geometry is further supported by the A s value of 156.8 × 10 -4 cm -1 determined by electron paramagnetic resonance (EPR) spectroscopy at 70 K. The d-d transition of 1 in [a]

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Riboflavin transporters (rft-1 and rft-2), orthologous to human riboflavin transporter-3 (hRVFT-3), are identified and characterized in Caenorhabditis elegans. However, studies pertaining to functional contribution of rft-2 in maintaining body homeostatic riboflavin levels and its regulation are very limited. In this study, the expression pattern of rft-2 at different life stages of C. elegans was studied through real-time PCR, and found to be consistent from larval to adult stages that demonstrate its involvement in maintaining the body homeostatic riboflavin levels at whole animal level all through its life. A possible regulation of rft-2 expression at mRNA levels at whole animal was studied after adaptation to low and high concentrations of riboflavin. Abundance of rft-2 transcript was upregulated in riboflavin-deficient conditions (10 nM), while it was downregulated with riboflavin-supplemented conditions (2 mM) as compared with control (10 meu M). Further, the 5'-regulatory region of the rft-2 gene was cloned, and transgenic nematodes expressing transcriptional rft-2 promoter::GFP fusion constructs were generated. The expression of rft-2 was found to be adaptively regulated in vivo when transgenic worms were maintained under different extracellular riboflavin levels, which was also mediated partly via changes in the rft-2 levels that directs towards the possible involvement of transcriptional regulatory events.

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