A high-throughput method to deliver targeted optogenetic stimulation to moving C. elegans populations

We present a high-throughput optogenetic illumination system capable of simultaneous closed-loop light delivery to specified targets in populations of moving Caenorhabditis elegans. The instrument addresses three technical challenges: It delivers targeted illumination to specified regions of the animal’s body such as its head or tail; it automatically delivers stimuli triggered upon the animal’s behavior; and it achieves high throughput by targeting many animals simultaneously. The instrument was used to optogenetically probe the animal’s behavioral response to competing mechanosensory stimuli in the the anterior and posterior gentle touch receptor neurons. Responses to more than 43,418 stimulus events from a range of anterior–posterior intensity combinations were measured. The animal’s probability of sprinting forward in response to a mechanosensory stimulus depended on both the anterior and posterior stimulation intensity, while the probability of reversing depended primarily on the anterior stimulation intensity. We also probed the animal’s response to mechanosensory stimulation during the onset of turning, a relatively rare behavioral event, by delivering stimuli automatically when the animal began to turn. Using this closed-loop approach, over 9,700 stimulus events were delivered during turning onset at a rate of 9.2 events per worm hour, a greater than 25-fold increase in throughput compared to previous investigations. These measurements validate with greater statistical power previous findings that turning acts to gate mechanosensory evoked reversals. Compared to previous approaches, the current system offers targeted optogenetic stimulation to specific body regions or behaviors with many fold increases in throughput to better constrain quantitative models of sensorimotor processing.

This study resents a new targeted illumination method for the nematode Caenorhabditis elegans, allowing delivery of optogenetic stimulation to specific body parts of many animals at once, automatically triggered by the animals’ behavior.     

Studies on beta-D-Gal(f)-(1-->4)-alpha-L-Rha(p) octyl analogues as substrates for mycobacterial galactosyl transferase activity

The biochemically unique structures of sugar residues in the outer cell wall of Mycobacterium tuberculosis (MTB) make the pathways for their biosynthesis and utilization attractive targets for the development of new and selective anti-tubercular agents. A cell-free assay system for galactosyltransferase activity using UDP[14C]Gal as the glycosyl donor, as well as an in vitro colorimetric broth micro-dilution assay system, were used to determine the activities of three beta-D-gal(f)(1-->4)-alpha-L-rham(p) octyl disaccharides as substrates and antimycobacterial agents respectively. The cell-free enzymatic studies using compounds 8 and 10 suggested that these disaccharides bind to and are effective substrates for a putative mycobacterial galactosyltransferase. The modified acceptor 8 was found to be a slower but prolonged binder as compared to the less substituted analogue 10 as evidenced by their Km and Vmax values. Moderate antimycobacterial activity was observed with compounds 8 and 9 against MTB H37Ra and three clinical isolates of Mycobacterium avium complex (MAC).     

VADAR: a web server for quantitative evaluation of protein structure quality

VADAR (Volume Area Dihedral Angle Reporter) is a comprehensive web server for quantitative protein structure evaluation. It accepts Protein Data Bank (PDB) formatted files or PDB accession numbers as input and calculates, identifies, graphs, reports and/or evaluates a large number (>30) of key structural parameters both for individual residues and for the entire protein. These include excluded volume, accessible surface area, backbone and side chain dihedral angles, secondary structure, hydrogen bonding partners, hydrogen bond energies, steric quality, solvation free energy as well as local and overall fold quality. These derived parameters can be used to rapidly identify both general and residue-specific problems within newly determined protein structures. The VADAR web server is freely accessible at http://redpoll.pharmacy.ualberta.ca/vadar.     

Solid-phase synthesis and bioevaluation of lupeol-based libraries as antimalarial agents

The use of the triterpenoid lupeol as a scaffold for the synthesis of lupeol-based libraries is described. Lupeol was anchored to a solid support (Rink amide/Sieber Amide) through aliphatic dicarboxylic acid moieties, which also served as a site for introducing diversity. The resulting polymer linked 3beta-O (resin-alkanoyl)-lup-20(29)-ene 3 was used to generate key intermediates 3beta-O (resin-alkanoyl)-30-bromo-lup-20(29)-ene 4 and 3beta-O (resin-alkanoyl)-30-amino-lup-20(29)-ene 6 for the generation of libraries based on disubstituted lupeol derivatives. A 96-member library was screened for its in-vitro antimalarial activity against Plasmodium falciparum.     

Baylis-Hillman reaction: convenient ascending syntheses and biological evaluation of acyclic deoxy monosaccharides as potential antimycobacterial agents

A series of acyclic deoxy carbohydrate derivatives from easily available carbohydrate enals 1, 2, 3 or 5 were prepared involving the Baylis-Hillman reaction. These newly formed carbohydrate based Baylis-Hillman adducts and their amino derivatives were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis H(37)R(v). Among the compounds evaluated for their antimycobacterial activity, compound (10) showed the desired activity in the range of 3.125 microg/mL.