Surface science of soft scorpionates

The chemisorption of the soft scorpionate Li[PhTmMe] onto silver and gold surfaces is reported. Surface enhanced Raman spectroscopy in combination with the Raman analysis of suitable structural models, namely, [Cu(κ3-S,S,S-PhTmMe)(PCy3)], [Ag(κ3-S,S,S-PhTmMe)(PCy3)], [Ag(κ2-S,S-PhTmMe)(PEt3)], and [Au(κ1-S-PhTmMe)(PCy3)], are employed to identify the manner in which this potentially tridentate ligand binds to these surfaces. On colloidal silver surface-enhanced Raman spectroscopy (SERS) spectra are consistent with PhTmMe binding in a didentate fashion to the surface, holding the aryl group in close proximity to the surface. In contrast, on gold colloid, we observe that the species prefers a monodentate coordination in which the aryl group is not in close proximity to the surface

Elucidation of the bonding of a near infrared dye to hollow gold nanospheres : a chalcogen tripod

Infrared surface enhanced Raman scattering (SERS) is an attractive technique for the in situ detection of nanoprobes in biological samples due to the greater depth of penetration and reduced interference compared to SERS in the visible region. A key challenge is to understand the surface layer formed in suspension when a specific label is added to the SERS substrate in aqueous suspension. SERS taken at different wavelengths, theoretical calculations, and surface-selective sum frequency generation vibrational spectroscopy (SFG-VS) were used to define the surface orientation and manner of attachment of a new class of infrared SERS label with a thiopyrylium core and four pendant 2-selenophenyl rings. Hollow gold nanospheres (HGNs) were used as the enhancing substrate and two distinct types of SERS spectra were obtained. With excitation close to resonance with both the near infrared electronic transition in the label (max 826 nm) and the plasmon resonance maximum (690 nm), surface enhanced resonance Raman scattering (SERRS) was obtained. SERRS indicates that the major axis of the core is near to perpendicular to the surface plane and SFG-VS obtained from a dried gold film gave a similar orientation with the major axis at an angle 64°-85° from the surface plane. Longer excitation wavelengths give SERS with little or no molecular resonance contribution and new vibrations appeared with significant displacements between the thiopyrylium core and the pendant selenophene rings. Analysis using calculated spectra with one or two rings rotated indicates that two rings on one end are rotated towards the metal surface to give an arrangement of two selenium and one sulphur atoms directly facing the gold structure. The spectra, together with a space filled model, indicate that the molecule is strongly adsorbed to the surface through the selenium and sulphur atoms in an arrangement which will facilitate layer formation

Comparison of Efficacy and Safety of Ciclosporin to Prednisolone in the Treatment of Erythema Nodosum Leprosum: Two Randomised, Double Blind, Controlled Pilot Studies in Ethiopia.

BACKGROUND: Erythema Nodosum Leprosum (ENL) is a serious complication of leprosy. It is normally treated with high dose steroids, but its recurrent nature leads to prolonged steroid usage and associated side effects. There is little evidence on the efficacy of alternative treatments for ENL, especially for patients who have become steroid resistant or have steroid side effects. These two pilot studies compare the efficacy and side effect profile of ciclosporin plus prednisolone against prednisolone alone in the treatment of patients with either new ENL or chronic and recurrent ENL. METHODS AND RESULTS: Thirteen patients with new ENL and twenty patients with chronic ENL were recruited into two double-blinded randomised controlled trials. Patients were randomised to receive ciclosporin and prednisolone or prednisolone treatment only. Patients with acute ENL had a delay of 16 weeks in the occurrence of ENL flare-up episode, with less severe flare-ups and decreased requirements for additional prednisolone. Patients with chronic ENL on ciclosporin had the first episode of ENL flare-up 4 weeks earlier than those on prednisolone, as well as more severe ENL flare-ups requiring 2.5 times more additional prednisolone. Adverse events attributable to prednisolone were more common that those attributable to ciclosporin. CONCLUSIONS: This is the first clinical trial on ENL management set in the African context, and also the first trial in leprosy to use patients' assessment of outcomes. Patients on ciclosporin showed promising results in the management of acute ENL in this small pilot study. But ciclosporin, did not appear to have a significant steroid-sparing effects in patients with chronic ENL, which may have been due to the prolonged use of steroids in these patients in combination with a too rapid decrease of steroids in patients given ciclosporin. Further research is needed to determine whether the promising results of ciclosporin in acute ENL can be reproduced on a larger scale

Universal surface-enhanced Raman tags : individual nanorods for measurements from the visible to the infrared (514 – 1064 nm)

Surface-enhanced Raman scattering (SERS) is a promising imaging modality for use in a variety of multiplexed tracking and sensing applications in biological environments. However, the uniform production of SERS nanoparticle tags with high yield and brightness still remains a significant challenge. Here, we describe an approach based on the controlled co-adsorption of multiple dye species onto gold nanorods to create tags that can be detected across a much wider range of excitation wavelengths (514 – 1064 nm) compared to conventional approaches that typically focus on a single wavelength. This was achieved without the added complexity of nanoparticle aggregation or growing surrounding metallic shells to further enhance the surface-enhanced resonance Raman scattering (SERRS) signal. Correlated Raman and scanning electron microscopy mapping measurements of individual tags were used to clearly demonstrate that strong and reproducible SERRS signals at high particle yields (>92 %) were readily achievable. The polyelectrolyte-wrapped nanorod-dye conjugates were also found to be highly stable as well as non-cytotoxic. To demonstrate the use of these universal tags for the multimodal optical imaging of biological specimens, confocal Raman and fluorescence maps of stained immune cells following nanoparticle uptake were acquired at several excitation wavelengths and compared with dark-field images. The ability to colocalize and track individual optically encoded nanoparticles across a wide range of wavelengths simultaneously will enable the use of SERS alongside other imaging techniques for the real-time monitoring of cell-nanoparticle interactions

Intracellular SERS nanoprobes for distinction of different neuronal cell types.

Distinction between closely related and morphologically similar cells is difficult by conventional methods especially without labeling. Using nuclear-targeted gold nanoparticles (AuNPs) as intracellular probes we demonstrate the ability to distinguish between progenitor and differentiated cell types in a human neuroblastoma cell line using surface-enhanced Raman spectroscopy (SERS). SERS spectra from the whole cell area as well as only the nucleus were analyzed using principal component analysis that allowed unambiguous distinction of the different cell types. SERS spectra from the nuclear region showed the developments during cellular differentiation by identifying an increase in DNA/RNA ratio and proteins transcribed. Our approach using nuclear-targeted AuNPs and SERS imaging provides label-free and noninvasive characterization that can play a vital role in identifying cell types in biomedical stem cell research

An Inserted α/β Subdomain Shapes the Catalytic Pocket of Lactobacillus johnsonii Cinnamoyl Esterase

Microbial enzymes produced in the gastrointestinal tract are primarily responsible for the release and biochemical transformation of absorbable bioactive monophenols. In the present work we described the crystal structure of LJ0536, a serine cinnamoyl esterase produced by the probiotic bacterium Lactobacillus johnsonii N6.2.We crystallized LJ0536 in the apo form and in three substrate-bound complexes. The structure showed a canonical α/β fold characteristic of esterases, and the enzyme is dimeric. Two classical serine esterase motifs (GlyXSerXGly) can be recognized from the amino acid sequence, and the structure revealed that the catalytic triad of the enzyme is formed by Ser(106), His(225), and Asp(197), while the other motif is non-functional. In all substrate-bound complexes, the aromatic acyl group of the ester compound was bound in the deepest part of the catalytic pocket. The binding pocket also contained an unoccupied area that could accommodate larger ligands. The structure revealed a prominent inserted α/β subdomain of 54 amino acids, from which multiple contacts to the aromatic acyl groups of the substrates are made. Inserts of this size are seen in other esterases, but the secondary structure topology of this subdomain of LJ0536 is unique to this enzyme and its closest homolog (Est1E) in the Protein Databank.The binding mechanism characterized (involving the inserted α/β subdomain) clearly differentiates LJ0536 from enzymes with similar activity of a fungal origin. The structural features herein described together with the activity profile of LJ0536 suggest that this enzyme should be clustered in a new group of bacterial cinnamoyl esterases