13C-NMR. Analysis of the Roxburghines

The ¹³C shifts of the alkaloids roxburghine B, C, D and E are determined. They confirm the following configurations for the last three bases: C(18α)-normal, C(18α)-pseudo and C(18β)-pseudo, respectively. Roxburghine B is shown to be a C(18β)-epi-allo isomer.     

Aggregation Modes of Chiral Diketopyrrolo[3,4-c]pyrrole Dyes in Solution and Thin Films

The chiroptical features of chiral diketopyrrolo[3,4-c]pyrrole (DPP) derivatives have been only marginally investigated to date. In this regard, we have synthesized ad hoc four chiral DPP dyes, functionalized with enantiopure alkyl groups from natural sources either on the lactam moieties or on the terminal positions of the π-conjugated backbone, to promote an efficient self-assembly into chiral supramolecular structures. For each of them, the aggregation modes has been investigated by absorbance and ECD spectroscopies in conditions of solution aggregation and on thin films, considering the effects of deposition technique (drop casting vs. spin coating) and post-deposition operations (solvent and thermal annealing). The effect of the structure of lateral π-conjugated units attached to the central DPP scaffold, as well as that of the position of the alkyl chiral group, has been assessed. ECD revealed superior capability, compared to absorbance spectroscopy, to provide information on the aggregation modes and to detect the possible co-existence of multiple aggregation pathways.     

Estimation of tire-road contact forces through a model-based approach employing strain measurements

Meccanica - The employment of intelligent tires to test the vehicle performances is ever-increasing in the last years. Many research activities have been made to correlate measurements provided by...     

A Lipophilic 4-Phenylbutyric Acid Derivative That Prevents Aggregation and Retention of Misfolded Proteins

Chemical chaperones prevent protein aggregation. However, the use of chemical chaperones as drugs against diseases due to protein aggregation is limited by the very high active concentrations (mm range) required to mediate their effect. One of the most common chemical chaperones is 4-phenylbutyric acid (4-PBA). Despite its unfavorable pharmacokinetic properties, 4-PBA was approved as a drug to treat ornithine cycle diseases. Here, we report that 2-isopropyl-4-phenylbutanoic acid ( 5 ) has been found to be 2–10-fold more effective than 4-PBA in several in vitro models of protein aggregation. Importantly, compound 5 reduced the secretion rate of autism-linked Arg451Cys Neuroligin3 (R451C NLGN3).     

An analysis method of the vortex-induced vibrations of a tethered sphere

Meccanica - Vortex-induced vibrations (VIV) in systems with more than one degree of freedom often present complex synchronization among the motion components, also hidden by the randomness that...     

Influence of the structural properties of poly(vinylidene fluoride) membranes on the heterogeneous nucleation rate of protein crystals

In this study, the influence of the morphological parameters of microporous poly(vinylidene fluoride) (PVDF) membranes on the heterogeneous nucleation rate of hen egg white lysozyme (HEWL) crystals has been investigated. Experiments have been carried out on membranes prepared by non-solvent-induced phase inversion method, using PVDF-co-hexafluoropropylene (Kynarflex 2800) and PVDF homopolymer (Kinar 460), and adding LiCl and poly(vinylpyrrolidone) (PVP) in order to modulate the pore structure. From a theoretical point of view, the free Gibbs energy balance for the formation of a critical nucleus has been adapted to nonporous surfaces, thus obtaining a mathematical correlation between the energy nucleation barrier, the membrane porosity, and the contact angle between protein solution and polymeric substrate. The energetic barrier to heterogeneous nucleation was found to increase at higher contact angles-according to the prediction of classical theory-and to decrease at higher porosity. For instance, the predicted deltaG(het)/deltaG(hom) ratio for PVDF-Kynarflex (PVP 2.5%) membrane with porosity of 0.11 was 0.30, 35% lower with respect to the value calculated by the Volmer equation for a dense polymeric matrix having the same contact angle (87.4 +/- 5.8 degrees). In addition, the effect of the membrane pore size, porosity, and thickness on the removal rate of solvent have been discussed. For example, the transmembrane flux through PVDF-Kynar (LiCl 5.0%) membrane was 12% inferior than the one measured under the same experimental conditions through PVDF-Kynarflex (LiCl 7.5%) membrane, the latter having similar pore size and thickness but higher porosity (0.44 vs 0.32). The possibility to achieve rapidly a high level of supersaturation is expected to increase the nucleation rate. In general, measurements performed during crystallization tests carried out at pH 4.5 in NaAc 0.05 M buffer with different precipitant (NaCl) concentrations agree with the predicted trends.     

Top‐down proteomics with a quadrupole time‐of‐flight mass spectrometer and collision‐induced dissociation

With slight modifications of the instrumental parameters, we demonstrate that satisfactory top‐down data can be obtained with collision‐induced dissociation (CID) tandem mass spectrometry on a quadrupole time‐of‐flight (qTOF) instrument not originally designed for this purpose. Protein identification is achieved with both N‐ and C‐terminal sequence tags and BLAST database searches. The accurate mass measurement of multiply charged fragment ions (mostly y and b‐type) supplements the limited set of cleavage sites and provides a high degree of sequence coverage (90–100%). Post‐translational modification issues can be addressed too. This approach might help those mass spectrometry (MS) core facilities that are not able to afford very high‐resolution instruments, thus expanding the benefits of top‐down protein analysis over the worldwide MS community. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of noncontact and fiber-based fluorescence-mediated tomography

We present a comparative experimental phantom study of fiber-based and noncontact fluorescence tomography with respect to quantitation and localization of reconstructed fluorescent inclusions in turbid media such as tissue. Noncontact acquisition is usually considered potentially superior to fiber-based techniques because of the availability of a large number of detector readouts through a CCD. Our results indicate, however, that noncontact acquisition itself might improve the quality of reconstructions significantly, even without increasing the number of detectors and thus keeping the inverse problem moderately complex.