216 research outputs found
Automated synthesis of monodisperse oligomers, featuring sequence control and tailored functionalization
Long, multifunctional sequence-defined oligomers were obtairred on solid support from a protecting-group-free two-step iterative protocol, based on the inherent reactivity of a readily available molecule containing an isocyanate and a thiolactone. Aminolysis of the latter entity with an amino alcohol liberates a thiol that reacts with an acrylate or acrylamide, present in the same medium. Subsequently, a new thiolactone can be reinstated by means of an alpha-isocyanato-gamma-thiolactone. Different acrylic compounds were used to incorporate diverse functionalities in the oligomers, which were built up to the level of decanters. The reaction conditions were closely monitored in order to fine-tune the applied strategy as well as facilitate the translation to an automated protocol
Co-exposure to extremely low-frequency electromagnetic fields and sound pressure in industrial environments: temporal measurements near power transformers
Infrared Multiple-Photon Dissociation Action Spectroscopy of the b(2)(+) Ion from PPG: Evidence of Third Residue Affecting b(2)(+) Fragment Structure
Infrared multiple-photon dissociation (IRMPD) action spectroscopy was performed on the b2 + fragment ion from the protonated PPG tripeptide. Comparison of the experimental infrared spectrum with computed spectra for both oxazolone and diketopiperazine structures indicates that the majority of the fragment ion population has an oxazolone structure with the remainder having a diketopiperazine structure. This result is in contrast with a recent study of the IRMPD action spectrum of the PP b2 + fragment ion from PPP, which was found to be nearly 100% diketopiperazine (Martens et al. Int. J. Mass Spectrom. 2015, 377, 179). The diketopiperazine b2 + ion is thermodynamically more stable than the oxazolone but normally requires a trans/cis peptide bond isomerization in the dissociating peptide. Martens et al. showed through IRMPD action spectroscopy that the PPP precursor ion was in a conformation in which the first peptide bond is already in the cis conformation and thus it was energetically favorable to form the thermodynamically-favored diketopiperazine b2 + ion. In the present case, solution-phase NMR spectroscopy and gas-phase IRMPD action spectroscopy show that the PPGprecursor ion has its first amide bond in a trans configuration suggesting that the third residue is playing an important role in both the structure of the peptide and the associated ring-closure barriers for oxazolone and diketopiperazine formation
Unraveling the Formation of Gelatin Nanospheres by Means of Desolvation
Gelatin nanoparticles (GNPs) have been widely studied
for a plethora of biomedical applications, but their formation
mechanism remains poorly understood, which precludes precise
control over their physicochemical properties. This leads to timeconsuming
parameter adjustments without a fundamental grasp of the
underlying mechanism. Here, we analyze and visualize in a timeresolved
manner the mechanism by which GNPs are formed during
desolvation of gelatin as a function of gelatin molecular weight and
type of desolvating agent. Through various analytical and imaging
techniques, we unveil a multistage process that is initiated by the formation of primary particles that are ∼18 nm in diameter (wet
state). These primary particles subsequently assemble into colloidally stable GNPs with a raspberry-like structure and a
hydrodynamic diameter of ∼300 nm. Our results create a basic understanding of the formation mechanism of gelatin nanoparticles,
which opens new opportunities for precisely tuning their physicochemical and biofunctional properties.Radboud University
Medical Cente
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