7 research outputs found
2015 Research & Innovation Day Program
A one day showcase of applied research, social innovation, scholarship projects and activities.https://first.fanshawec.ca/cri_cripublications/1002/thumbnail.jp
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers âŒ99% of the euchromatic genome and is accurate to an error rate of âŒ1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
Critical Fluctuations in Liquid-Liquid Extraction Organic Phases Controlled by Extractant and Diluent Molecular Structure
Extractant aggregation in liquid-liquid extraction organic phases impacts extraction energetics and is related to the deleterious efficiency-limiting liquid-liquid phase transition known as third phase formation. Using small angle x-ray scattering, we find that structural heterogeneities across a wide range of compositions in binary mixtures of malonamide extractants and alkane diluents are well described by Ornstein-Zernike scattering. This suggests that structure in these simplified organic phases originates from the critical point associated with the liquid-liquid phase transition. To confirm this, we measure the temperature dependence of the organic phase structure, finding critical exponents consistent with the 3D Ising model. Molecular dynamics simulations were also consistent with this mechanism for extractant aggregation. Due to the absence of water or any other polar solutes required to form reverse-micellar-like nanostructures, these fluctuations are inherent to the binary extractant/diluent mixture. Our previous work found pseudobinary critical fluctuations near the critical point for more complex organic phases with extracted polar solutes, including water, acid and metal ions. Taken together, these results suggest this mechanism for explaining organic phase aggregation may dominate over a wide range of conditions encountered in practical liquid-liquid extraction organic phases. We also show how the molecular structure of the extractant and diluent modulate these critical concentration fluctuations by shifting the critical temperature: critical fluctuations are suppressed by increasing extractant alkyl tail lengths or decreasing diluent alkyl chain lengths. This is consistent with how extractant and diluent molecular structure are known to impact metal and acid loading capacity in many-component LLE organic phases, suggesting phase behavior of practical systems may be effectively studied in simplified organic phases. Overall, the explicit connection between molecular structure, aggregation and phase behavior demonstrated here will enable the design of more efficient separations processes
Molecular Dynamics Simulations as a Tool for Accurate Determination of Surfactant Micelle Properties
Molecular
dynamics (MD) simulations were used to characterize the
equilibrium size, shape, hydration, and self-assembly of dodecylphosphocholine
(DPC) and dodecyl-ÎČ-D-maltoside (DDM) micelles. We show that
DPC molecules self-assemble to form micelles with sizes within the
range reported in the experimental literature. The equilibrium shape
of DPC and DDM micelles as well as associated micellar radii are in
agreement with small-angle X-ray scattering (SAXS) experiments and
theoretical packing parameters. In addition, we show that hydration
of the micelle interior is limited; however, flexibility of the acyl
chains leads to dynamic encounters with the solvated outer shell of
the micelle, providing an explanation for long-standing differences
in models of micelle hydration. Altogether, our results provide fundamental
understanding of physical characteristics of micelles that can be
utilized to study other types of detergents and proteomicelle complexes
Unveiling the mechanism of the photocatalytic reduction of CO 2 to formate promoted by porphyrinic Zr-based metalâorganic frameworks
International audienceA complete picture of the reaction mechanism driving the photocatalytic reduction of CO 2 into formate promoted by the Zr-based porphyrinic MOF-545 in CH 3 CN/TEOA solutions is provided for the first time by combining experimental and computational approaches
Role of Surface-Grafted Polymers on Mechanical Reinforcement of MetalâOrganic FrameworkâPolymer Composites
Utilizing metalâorganic frameworks (MOFs) as reinforcing
fillers for polymer composites is a promising strategy because of
the low density, high specific modulus, and tunable aspect ratio (AR).
However, it has not been demonstrated for the MOF-reinforced polymer
composite using MOFs with high AR and polymer-grafted surface, both
of which are extremely important factors for efficient load transfer
and favorable particleâmatrix interaction. To this end, we
designed an MOFâpolymer composite system using high AR MOF
PCN-222 as the mechanical reinforcer. Moreover, we developed a synthetic
route to graft poly(methyl methacrylate) (PMMA) from the surface of
PCN-222 through surface-initiated atomic transfer radical polymerization
(SI-ATRP). The successful growth of PMMA on the surface of PCN-222
was confirmed via proton nuclear magnetic resonance
and infrared spectroscopy. Through thermogravimetric analysis, the
grafting density was found to be 0.18 chains/nm2. The grafted
polymer molecular weight was controlled ranging from 50.3 to 158 kDa
as suggested by size exclusion chromatography. Finally, we fabricated
MOFâpolymer composite films by the doctor-blading technique
and measured the mechanical properties through the tension mode of
dynamic mechanical analysis. We found that the mechanical properties
of the composites were improved with increasing grafted PMMA molecular
weight. The maximum reinforcement, a 114% increase in Youngâs
modulus at 0.5 wt % MOF loading in comparison to pristine PMMA films,
was achieved when the grafted molecular weight was higher than the
matrix molecular weight, which was in good agreement with previous
literature. Moreover, our composite presents the highest reinforcement
measured via Youngâs modulus at low weight
loading among MOF-reinforced polymer composites due to the high MOF
AR and enhanced interface. Our approach offers great potential for
lightweight mechanical reinforcement with high AR MOFs and a generalizable
grafting-from strategy for porphyrin-based MOFs