Oligonucleotide-gold nanoparticle (OGN) conjugates are powerful tools for the detection of target DNA sequences due to the unique properties conferred upon the oligonucleotide by the nanoparticle. Practically all the research and applications of these conjugates have used gold nanoparticles to the exclusion of other noble metal nanoparticles. Here we report the synthesis of oligonucleotide-silver nanoparticle (OSN) conjugates and demonstrate their use in a sandwich assay format. The OSN conjugates have practically identical properties to their gold analogues and due to their vastly greater extinction coefficient both visual and absorption analyses can occur at much lower concentrations. This is the first report of OSN conjugates being successfully used for target DNA detection and offers improved sensitivity which is of interest to a range of scientists.

Enantiomerically pure chiral amines are valuable synthetic intermediates, particularly for the preparation of pharmaceutical compounds. Traditionally, chiral amines have been obtained by resolution-based procedures, for example, by kinetic resolution of a racemate using an enzyme [1,2] or crystallization of a diastereomer using a chiral acid to form a salt. [3] Increasingly, there is a desire to develop asymmetric approaches, or their equivalents, which can in principal deliver the product in 100 % yield and 100 % ee. For example, transaminases have been utilized for the conversion of COMMUNICATIONS

Enantiomerically pure chiral amines are of increasing value in organic synthesis, especially as resolving agents, [1] chiral auxiliaries/chiral bases, [2] and catalysts for asymmetric synthesis. [3] In addition, chiral amines often possess pronounced biological activity in their own right and hence are in demand as intermediates for agrochemicals and pharmaceuticals. [4] Current methods for the preparation of enantiomerically pure chiral amines are largely based upon the resolution of racemates, either by recrystallization of diastereomeric salts [5] or by enzyme-catalyzed kinetic resolution of racemic substrates using lipases and acylases.[6] To develop more efficient methods, attention is turning towards asymmetric approaches or their equivalent, for example, the asymmetric hydrogenation of imines [7] or the conversion of ketones into amines by using transaminases.[8] Attempts to develop dynamic kinetic resolutions, which employ enzymes in combination with transition-metal catalysts, have unfortunately been hampered by the harsh conditions required to racemize amines.[9]Recently we reported a novel catalytic method for the preparation of optically active chiral amines by deracemization of the corresponding racemic mixture (Figure 1).[10] The deracemization approach relies upon coupling an enantioselective amine oxidase with a nonselective reducing agent to effect stereoinversion of the S to R enantiomer via the intermediate achiral imine.The S enantiomer selective amine oxidase used for the deracemization of (R/S)-a-methylbenzyl amine was identified from a library of variants of the wild-type enzyme, from Aspergillus niger, by using a high-throughput colorimetric screen to guide selection.[10] The library of variants was generated by randomly mutating the plasmid harboring the amine oxidase gene by using the E. coli XL1-Red mutator strain. Using (S)-a-methylbenzylamine as the target substrate we were able to identify a variant (Asn336Ser) that possessed significantly improved catalytic activity (47 fold) and enantioselectivity (sixfold) towards this particular substrate compared to the wild type enzyme. To explore the opportunities for using this variant amine oxidase to deracemize other racemic chiral amines we decided to undertake a more detailed study of its substrate specificity. Herein we show that the Asn336Ser variant possesses broad substrate specificity and high enantioselectivity towards a wide range of chiral amines.Prior to carrying out further studies with the Asn336Ser amine oxidase, an additional mutation was introduced into the sequence (Met348Lys) that resulted in a variant enzyme (hereafter referred to as Asn336Ser) with higher specific activity and expression levels although its substrate specificity appeared unchanged (data not shown). Incorporation of an N-terminal histidine tag into the amine oxidase allowed facile purification of both the wild-type and Asn336Ser variant in one step, by a nickel-affinity column, to yield protein of > 90 % purity as evidenced by gel electrophoresis (Figure ...

A new approach for the detection of DNA using surface enhance resonance Raman scattering (SERRS) is reported. The majority of existing techniques use fluorescence spectroscopy with advanced probe design to provide information on the identity of specific DNA sequences down to single base resolution. A new approach to the labelling of DNA is discussed which uses Michael addition to couple thiolated DNA to dye labels specifically designed to attach to silver surfaces. When combined with existing strategies for sensitive detection of DNA using commercially available labels, a new class of biomolecular probe known as a SERRS Beacon was produced. The detection techniques of fluorescence and surface enhanced resonance Raman scattering (SERRS) are combined to give a sensitive and selective system for use in the development and creation of novel assays for specifically defined targets. It demonstrates improved potential for multiplexing analysis.

Enantiomerically pure chiral amines are valuable synthetic intermediates, particularly for the preparation of pharmaceutical compounds. Traditionally, chiral amines have been obtained by resolution-based procedures, for example, by kinetic resolution of a racemate using an enzyme [1,2] or crystallization of a diastereomer using a chiral acid to form a salt. [3] Increasingly, there is a desire to develop asymmetric approaches, or their equivalents, which can in principal deliver the product in 100 % yield and 100 % ee. For example, transaminases have been utilized for the conversion of ZUSCHRIFTEN