Spatially Resolved Solid-State 1H NMR for Evaluation of Gradient-Composition Polymeric Libraries.
Summary of "Spatially Resolved Solid-State 1H NMR for Evaluation of Gradient-Composition Polymeric Libraries."
Polyurethane libraries consisting of films with composition gradients of aliphatic polyisocyanate and hydroxy-terminated polyacrylate resin was characterized using methods of 1H NMR micro-imaging (i.e., MRI) and solid-state NMR. Molecular mobilities and underlying structural information were extracted as a function of the relative content of each of the two components. Routine NMR micro-imaging using the spin-echo sequence only allows investigations of transverse relaxation of magnetization at echo times > 2 ms. A single-exponential decay was found, which is likely due to free, non-crosslinked polymer chains. The mobility of these chains decreases with increasing content of the aliphatic polyisocyanate. The concept of a 1D NMR profiler is introduced as a novel modality for library screening, which allows the convenient measurement of static solid-state NMR spectra as a function of spatial location along a library sample that is repositioned in the rf coil between experiments. With this set-up the complete transverse relaxation function was measured using Bloch decays and spin echoes. For all positions within the gradient-composition film, relaxation data consisted of at least three components that were attributed to a rigid highly crosslinked resin, an intermediate crosslinked but mobile constituent, and the highly mobile free polymer chains (the latter is also detectable by MRI). Analysis of this overall relaxation function measured via Bloch decays and Hahn echoes revealed only minor changes in the mobilities of the individual fractions. Findings with respect to the most mobile components are consistent with the results obtained by NMR micro-imaging. The major effect is the significant increase in the rigid-component fraction with the addition of the hydroxy-terminated polyacrylate resin.
This article was published in the following journal.
Name: ACS combinatorial science
Medical and Biotech [MESH] Definitions
Centrifugation, Density Gradient
Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
A technique used to separate particles according to their densities in a continuous density gradient. The sample is usually mixed with a solution of known gradient materials and subjected to centrifugation. Each particle sediments to the position at which the gradient density is equal to its own. The range of the density gradient is usually greater than that of the sample particles. It is used in purifying biological materials such as proteins, nucleic acids, organelles, and cell types.
The quality or state of being wettable or the degree to which something can be wet. This is also the ability of any solid surface to be wetted when in contact with a liquid whose surface tension is reduced so that the liquid spreads over the surface of the solid.
A 15 kD "joining" peptide that forms one of the linkages between monomers of IMMUNOGLOBULIN A or IMMUNOGLOBULIN M in the formation of polymeric immunoglobulins. There is one J chain per one IgA dimer or one IgM pentamer. It is also involved in binding the polymeric immunoglobulins to POLYMERIC IMMUNOGLOBULIN RECEPTOR which is necessary for their transcytosis to the lumen. It is distinguished from the IMMUNOGLOBULIN JOINING REGION which is part of the IMMUNOGLOBULIN VARIABLE REGION of the immunoglobulin light and heavy chains.
Receptors, Polymeric Immunoglobulin
Specialized Fc receptors (RECEPTORS, FC) for polymeric immunoglobulins, which mediate transcytosis of polymeric IMMUNOGLOBULIN A and IMMUNOGLOBULIN M into external secretions. They are found on the surfaces of epithelial cells and hepatocytes. After binding to IMMUNOGLOBULIN A, the receptor-ligand complex undergoes endocytosis, transport by vesicle, and secretion into the lumen by exocytosis. Before release, the part of the receptor (SECRETORY COMPONENT) that is bound to IMMUNOGLOBULIN A is proteolytically cleaved from its transmembrane tail. (From Rosen et al., The Dictionary of Immunology, 1989)
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