5-Exo-dig cyclocondensation of alk-3-yn-1-ones with hydrazines, in the presence of montmorillonite K-10, provides an effective method with a high atom economy for the synthesis of diversely ...1,3,5-trisubstituted pyrazoles. The microwave-accelerated reaction proceeds in the absence of solvent and leads to 5-benzyl substituted pyrazoles with good yields (72-91%). The regiochemistry of the process was confirmed by the X-ray crystallographic structure determination of 1-(2-fluorophenyl)-5-(4-methylbenzyl)-3-phenyl-1H-pyrazole.
5-
Exo-dig
cyclocondensation of alk-3-yn-1-ones with hydrazines, in the presence of montmorillonite K-10, provides an effective method with a high atom economy for the synthesis of diversely ...1,3,5-trisubstituted pyrazoles. The microwave-accelerated reaction proceeds in the absence of solvent and leads to 5-benzyl substituted pyrazoles with good yields (72-91%). The regiochemistry of the process was confirmed by the X-ray crystallographic structure determination of 1-(2-fluorophenyl)-5-(4-methylbenzyl)-3-phenyl-1
H
-pyrazole.
Tandem condensation/5-
exo-dig
cyclization reactions of propargyl ketone with hydrazines gives easy access to 1,3,5-unsymetrically substituted pyrazoles.
Hydration in the minor groove of B-form DNA influences the stability and conformation of duplex DNA. An analogue nucleoside that attempts to mimic the N3-hydrated adenine was designed and ...synthesized. Obtaining the modified adenine was a significant synthetic effort. The attempted incorporation of the new analogue in a DNA strand yielded inconclusive results, and further tests are ongoing. The incorporation of the new modified purine in a DNA duplex may be useful for a better understanding of the hydration of B-form DNA.
Thesis advisor: Larry W. McLaughlin
Hydration in the minor groove of B-form DNA influences the stability and conformation of duplex DNA. An analogue nucleoside that attempts to mimic the N3-hydrated ...adenine was designed and synthesized. Obtaining the modified adenine was a significant synthetic effort. The attempted incorporation of the new analogue in a DNA strand yielded inconclusive results, and further tests are ongoing. The incorporation of the new modified purine in a DNA duplex may be useful for a better understanding of the hydration of B-form DNA.
Thesis (MS) — Boston College, 2012.
Submitted to: Boston College. Graduate School of Arts and Sciences.
Discipline: Chemistry.
Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm ...growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.
We present a strategy for the skeletal editing of diamondoid structures to selectively displace methylene for heteroatom moieties in the carbon framework. This constitutes a synthetic approach to ...doping diamond-like structures with electron donor dopants (O, N, and S). The key steps involve two subsequent retro-Barbier fragmentations followed by cage reconstruction in the presence of a dopant. Remarkably, the incorporation of n-dopants reduces the strain of the diamondoid cage as shown through homodesmotic equations.
Following the fertilization of an egg by a single sperm, the egg coat or zona pellucida (ZP) hardens and polyspermy is irreversibly blocked. These events are associated with the cleavage of the ...N-terminal region (NTR) of glycoprotein ZP2, a major subunit of ZP filaments. ZP2 processing is thought to inactivate sperm binding to the ZP, but its molecular consequences and connection with ZP hardening are unknown. Biochemical and structural studies show that cleavage of ZP2 triggers its oligomerization. Moreover, the structure of a native vertebrate egg coat filament, combined with AlphaFold predictions of human ZP polymers, reveals that two protofilaments consisting of type I (ZP3) and type II (ZP1/ZP2/ZP4) components interlock into a left-handed double helix from which the NTRs of type II subunits protrude. Together, these data suggest that oligomerization of cleaved ZP2 NTRs extensively cross-links ZP filaments, rigidifying the egg coat and making it physically impenetrable to sperm.
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•Post-fertilization cleavage of zona pellucida (ZP) subunit ZP2 makes it oligomerize•Premature ZP2 oligomerization causes infertility by impairing sperm penetration of ZP•A native egg coat fragment structure sheds light on heteromeric ZP filament assembly•Cleaved ZP2 cross-links ZP filaments to harden the egg coat and prevent polyspermy
Post-fertilization cleavage of the egg zona pellucida (ZP) subunit ZP2 triggers its oligomerization, which in turn cross-links the filaments that make up the ZP. By tightening its mesh, this hardens the egg coat matrix and hinders the penetration of further sperm, thereby ensuring a permanent block to polyspermy.
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