Binding groups biology

Ab initio and semiempirical methods have been applied to the interpretation of many aspects of dithiolene chemistry electronic spectra, ESR, Mossbauer, XPS, charge distributions, redox properties, reaction mechanisms, metal binding in biological systems and ligand-exchange behavior. We shall focus our attention on the theoretical deductions of some representative research groups. For computational details, the reader is referred to the original papers and references therein. 

Table 2 Likely Binding Groups for Biologically Important Metal Ions...

The reaction of tripyrranes with pyrrolecarboxaldehyde in the presence of TFA catalyst followed by oxidation with chloranil results in a simultaneous oxidative coupling and condensation to generate a meso-free corrole <02OL4233>. A fluorescence receptor based on triaza-18-crown-6 ether combined with two /V-guanidinium groups (and one A-anthracen-9-ylmethyl moiety) could bind several biologically important amino acids in aqueous methanol... 

The spectral characteristics of the Group 12 metal ions binding to biological ligands are dominated by the LMCT transitions from the electron-donating hgand atom to the d-shell of the metal atom. These transitions occur in the near-UV region of the spectrum, from 230 nm to 360 mn. 

PMMA itself does not possess ready-to-use fiinctional groups for covalent binding with biological molecules. The amine-terminated PMMA were often produced by immersing the freshly cleaned PMMA substrate into a 1.0 M ethylenediamine in dimethyl sulfoxide (DMSO) solution for 15 min at room temperature (115) or coated with a thin layer of polyethyleneimine (PEI) or polyallylamine hydrochloride (PAH). This was first treated in 1 N sodium hydroxide (NaOH) solution at 55 C for 30 min and then immersed in a PEI or PAH solution (0.2%, pH 7) at room temperature for 1 h (117). Tsai and Lin (2005) demonstrated that PEI-derivatized PMMA was used for the determination of alpha-fetoprotein by quartz crystal microbalance (QCM) (118). Furthermore, the amine-terminated PMMA could be generated by reacting with 10% hexamethylene diamine (HMD) (reaction shown in scheme 8.2) or 1,3-diaminopropane (DAP) in 100 mM borate buffer pH 11.5 for 2 h (119) or exposing to -lithioethylenediamine (120) (reaction shown in scheme 8.3). 

As seen in the previous work, arsenic will bind to biological molecules and hinder enzymic activity. The main mode of action seems to be to bind to systems that contain thiol as a functional group. For proteins, this can be either cysteine or cofactors that contain thiol groups. Our recent research efforts have elucidated the interaction with some of the target molecules. The arsenical that we have used is phenyldichloroarsine, an organic trivalent species that can penetrate cells easily. 

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