Protein adsorption in static microsystems: effect of the surface to volume ratio

A numerical model for the adsorption kinetics of proteins on the walls of a microchannel has been developed using the finite element method (FEM) to address the coupling with diffusion phenomena in the restricted microchannel volume. Time evolutions of the concentration of one species are given, both in solution and on the microchannel walls. The model illustrates the adsorption limitation sometimes observed when the microdimensions of these systems induce a global depletion of the bulk solution. A new non-dimensional parameter is introduced to predict the final value of the coverage of any microsystem under static adsorption. A working curve and a criteria (h/K[Gamma](max) > 10) are provided in order to choose, for given adsorption characteristics, the value of the volume-to-surface ratio (i.e. the channel height h) avoiding depletion effects on the coverage (relative coverage greater than 90% of the theoretical one). Simulations were compared with confocal microscopy measurements of IgG antibody adsorption on the walls of a PET microchannel. The fit of the model to the experimental data show that the adsorption is under apparent kinetic control.     

Heavy group 14 1,(n+2)-dimetallabicyclo[n.n.n]alkanes and 1,(n+2)-dimetalla[n.n.n]propellanes: are they all realistic synthetic targets?

[n.n.n]Propellanes and bicyclo[n.n.n]alkanes (1相似文献   

The Yellow Polymorphs of Mercuric Iodide (HgI2)

HgI₂ crystallizes under ambient conditions from various solvents and by sublimation into three concomitant polymorphs whose colors are red, orange, and yellow. The orange and yellow phases are metastable and transform into the red phase when touched. A phase transition from red to yellow occurs at 400 K. The reverse transition from yellow to red shows a huge hysteresis. We established that the structures of the metastable yellow^M phase (determined by single‐crystal X‐ray diffraction) and the high‐temperature yellow^HT phase (determined by powder synchrotron X‐ray diffraction and second‐harmonic generation) are different, albeit closely related. Both show analogous packings of I? Hg? I molecules, which are straight in the first and bent with an angle of ca. 160° in the second. The red and orange phases are tetrahedral semiconductor structures that sublime even at room temperature. The growth of the yellow^M phase from 2‐chloroethanol and the kinetics of the reconstructive phase transition red to yellow^HT and back were studied by optical microscopy, Raman spectroscopy in solution, luminescence, and powder synchrotron X‐ray diffraction as a function of time at various temperatures. Both yellow phases grow by accretion of HgI₂ molecules, present in the solution or liberated from the red crystals, on the surface of the crystal. In contrast, the reverse transformation from yellow to red occurs in the bulk of the crystal, presumably by migration of Hg in the packing of I and subsequent rearrangement of I. The displacement parameters of Hg in both structures are considerably larger than those of I and apparently not dominated by disorder effects.     

An amino acid based system for CO2 capture and catalytic utilization to produce formates

Herein, we report a novel amino acid based reaction system for CO₂ capture and utilization (CCU) to produce formates in the presence of the naturally occurring amino acid l-lysine. Utilizing a specific ruthenium-based catalyst system, hydrogenation of absorbed carbon dioxide occurs with high activity and excellent productivity. Noteworthy, following the CCU concept, CO₂ can be captured from ambient air in the form of carbamates and converted directly to formates in one-pot (TON > 50 000). This protocol opens new potential for transforming captured CO₂ from ambient air to C1-related products.

A novel amino acid based reaction system for CO₂ capture and utilization (CCU) to produce formates is presented applying a ruthenium-based catalyst. Noteworthy, CO₂ can be captured from ambient air and converted to formates in one-pot (TON > 50 000).     

Expedient protocol for solid-phase synthesis of secondary and tertiary amines

[reaction: see text] An expedient solid-phase synthetic approach to secondary and tertiary amines was developed. The protocol employs conversion of resin-bound amino alcohols to the corresponding iodides, followed by iodide displacement with primary or secondary amines or with unprotected amino alcohols. This two-step procedure, affording products in good to excellent yields, is suitable for solid-phase synthesis of polyamines.     

A study of the Arrhenius behavior of the co-precipitation of radium, barium and strontium sulfate

Co-precipitation of radium, barium and strontium is an important process in many contexts, such as uranium mining, oil extraction and in the safety assessment of a final repository for used nuclear fuel. Co-precipitation to a solid solution is possible since radium, barium and strontium act as chemical analogues. In this work the co-precipitation of radium, barium and strontium was studied and the kinetic behavior of the co-precipitation process was investigated. It was shown that radium, barium and strontium co-precipitate congruently and that the precipitation followed an Arrhenius behavior and the Arrhenius parameters for the systems was determined. When studying the differences of the Arrhenius constants by using a student t test (95 % confidence interval) it was observed that the only significant difference in the activation energy, E _a, is between radium and barium and between radium and strontium respectively, the pure strontium having the larger activation energy in comparison. This is most likely coupled to the metal ion size; since the hydration waters are more strongly bound, which leads to them having a slower exchange rate, which in turn effects the rate of co-precipitation to the metal these reactions will be slower.     

A convenient One-Pot Synthesis of an Unsymmetrical Propane-1,3-diamine BRL 61010A

The one-pot condensation of N-methylhomoveratrylamine with acrolein followed by in situ reductive amination with 3,4-dimethoxyaniline to give an unsymmetrical propane 1,3-diamine in excellent yield is described.     

[B(O–C6H4–CN)4]– based Silver and Copper Coordination Polymers

A series of new coordination polymers bearing the [B(O–C₆H₄–CN)₄]^– anion was synthesized. Two new, one dimensional coordination frameworks of the type M[B(O–C₆H₄–CN)₄] (M = Ag, Cu) were obtained by salt metathesis. The reactivity towards organic Lewis‐bases was studied. The reaction with bidentate ligands yielded two dimensional networks with the general formula [M(L)][B(O–C₆H₄–CN)₄] {L = 2,2′‐bipyridine, 4,4′‐bipyridine, 1,2‐bis(pyridyl)ethane, 1,4‐diazabicyclo[2.2.2]octane}. The synthesis, properties and single crystal structure are reported.