Miniaturized, multi-spectral optics for tissue differentiation

Identification of tumour margins during resection of the brain is critical for improving the post-operative outcomes. Present research aims to develop a miniaturized, optical system for simultaneous measurement of DRS and auto-fluorescence for brain tumour detection

Silicon Photomultiplier—A High Dynamic Range, High Sensitivity Sensor for Bio-Photonics Applications

This work is an overview of silicon photomultipliers (SiPMs) with a view to defining their importance for bio-photonic and clinical applications. SiPMs are benchmarked against other common photodetectors, namely, PIN diodes and avalanche photodetectors (APDs) and are compared with respect to important circuit design parameters. It will be shown that careful selection of the design bias voltage, overvoltage, gain defining components and device integration to micro-optics can allow SiPM detectors to achieve considerable sensitivity for auto-fluorescence (AF) detection and a wide dynamic range at low optical powers (~1 pW to ~4 μW). The SiPM has a manageable bias voltage (~25 V to ~30 V DC) for systems integration, and with optimised sensitivity it will enhance bio-photonic research in the area of AF to detect intraoperatively, for example, brain tumour margins

Chromatin compaction by human MeCP2 assembly of novel secondary chromatin structures in the absence of DNA methylation

MeCP2 is a transcriptional repressor that contains an N-terminal methylated DNA-binding domain, a central transcription regulation domain, and a C-terminal domain of unknown function. Whereas current models of MeCP2 function evoke localized recruitment of histone deacetylases to specific methylated regions of the genome, it is unclear whether MeCP2 requires DNA methylation to bind to chromatin or whether MeCP2 binding influences chromatin structure in the absence of other proteins. To address these issues, we have characterized the complexes formed between MeCP2 and biochemically defined nucleosomal arrays. At molar ratios near 1 MeCP2/nucleosome, unmethylated nucleosomal arrays formed both extensively condensed ellipsoidal particles and oligomeric suprastructures. Furthermore, MeCP2-mediated chromatin compaction occurred in the absence of monovalent or divalent cations, in distinct contrast to all other known chromatin-condensing proteins. Analysis of specific missense and nonsense MeCP2 mutants indicated that the ability to condense chromatin resides in region(s) of the protein other than the methylated DNA-binding domain. These data demonstrate that MeCP2 assembles novel secondary chromatin structures independent of DNA modification and suggest that the ability of MeCP2 to silence chromatin may be related in part to its effects on large-scale chromatin organization