Glycosylation and metastases

The change of cellular glycosylation is one of the key events in malignant transformation and neoplastic progression, and tumor‐related glycosylation alterations are promising targets in both tumor diagnosis and therapy. Both malignant transformation and neoplastic progression are the consequence of gene expression alterations and alterations in protein expression. Micro environmental factors such as extracellular matrix (ECM) also play an important role in their growth and metastasis. Tumor‐associated glycans are important biomarker candidates for cancer diagnosis and prognosis, and analytical methods for their detection were developed recently. Glycoproteomics that use mass spectrometry for identification of cancer antigens and structural analysis of glycans play a key role in the investigation of changes of glycosylation during malignant transformation and tumor development and metastasis. Deep understanding of glycan remodeling in cancer and the role of glycosyltransferases that are involved in this process will require a detailed profiling of glycosylation patterns of tumor cells, and corresponding analytical methods for their detection were developed.     

Hydrogen bonding in two benzene‐1,2‐diaminium pyridine‐2‐carboxylate salts and a cocrystal of benzene‐1,2‐diamine and benzoic acid

The isostructural salts benzene‐1,2‐diaminium bis(pyridine‐2‐carboxylate), 0.5C₆H₁₀N₂²⁺·C₆H₄NO₂^?, (1), and 4,5‐dimethylbenzene‐1,2‐diaminium bis(pyridine‐2‐carboxylate), 0.5C₈H₁₄N₂²⁺·C₆H₄NO₂^?, (2), and the 1:2 benzene‐1,2‐diamine–benzoic acid cocrystal, 0.5C₆H₈N₂·C₇H₆O₂, (3), are reported. All of the compounds exhibit extensive N—H…O hydrogen bonding that results in interconnected rings. O—H…N hydrogen bonding is observed in (3). Additional π–π and C—H…π interactions are found in each compound. Hirshfeld and fingerprint plot analyses reveal the primary intermolecular interactions and density functional theory was used to calculate their strengths. Salt formation by (1) and (2), and cocrystallization by (3) are rationalized by examining pK_a differences. The R₂²(9) hydrogen‐bonding motif is common to each of these structures.     

Phenomenological modeling and intensification of texturing/grinding-assisted solvent oil extraction: case of date seeds (Phoenix dactylifera L.)

Accelerated Solvent Extraction (ASE) and Dynamic Maceration (DM) were used with n-hexane to study the extraction of oil from date seed powders with different particle sizes. The intensification was studied with instant controlled pressure drop (DIC) as texturing pretreatment. DM yields increased from 4.57% to 10.49 ± 0.05% dry–dry basis (ddb) when particle size decreased from 1.4 to 0.2 mm. For coarsely grounded seed powder, ASE oil yields were 11.35 ± 0.05% ddb and 14.15% ddb for untreated and DIC date-seeds, respectively. Optimized DIC pretreatment allowed the smallest particle size powder to get 15.2 ± 0.05% ddb as ASE yields, while the 2-h DM yields increased from 4.67 to 11.62 ± 0.05% ddb for particle size decreased from 1.4 to 0.2 mm, respectively. Fundamental analysis of various powders was achieved through washing–diffusion phenomenological model. DIC texturing implied higher washing stage, with relative starting accessibility %δY_s of 70% against 55% for untreated particles. Consequently, the diffusion stage time was dramatically reduced, without great modification of effective diffusivity D_eff value. Therefore, DIC ground seeds greatly enhanced the mass transfer mechanism. The evaluation of starting accessibility δY_s enables to establish an empirical relationship between δY_s and particle diameter δY_s = f(D). Finally, DIC texturing did not imply any modification of the lipid profile.     

Europium-151 Mössbauer effect study of relaxation in two bi(pentamethylcyclopentadienyl) europium(II) complexes

Europium-151 Mössbauer spectra of two bis(pentamethylcyclopentadienyl) europium complexes have been recorded at 78K. The broad spectra with linewidths of 14.2 and 11.6 mm/s, and with isomer shifts of –12.5 and –12.8 mm/s, relative to EuF₃ may be understood in terms of spherical relaxation of the effective hyperfine field.     

Subunit modification and association in VR1 ion channels

Background  

The capsaicin (vanilloid) receptor, VR1, is an agonist-activated ion channel expressed by sensory neurons that serves as a detector of chemical and thermal noxious stimuli.     

Whitham Equations, Bergman Kernel and Lax—Levermore Minimizer

We study multiphase solutions of the Whitham equations. The Whitham equations describe the zero dispersion limit of the Cauchy problem for the Korteweg—de Vries (KdV) equation. The zero dispersion solution of the KdV equation is determined by the Lax—Levermore minimization problem. The minimizer is a measurable function on the real line. When the support of the minimizer consists of a finite number of disjoint intervals to be determined, the minimization problem can be reduced to a scalar Riemann Hilbert (RH) problem. For each fixed x and t 0, the end-points of the contour are determined by the solution of the Whitham equations. The Lax—Levermore minimizer and the solution of the Whitham equations are described in terms of a kernel related to the Bergman kernel. At t = 0 the support of the minimizer consists of one interval for any value of x, while for t > 0, the number of intervals is larger than one in some regions of the (x,t) plane where the multiphase solutions of the Whitham equations develop. The increase of the number of intervals happens whenever the solution of the Whitham equations has a point of gradient catastrophe. For a class of smooth monotonically increasing initial data, we show that the support of the Lax—Levermore minimizer increases or decreases the number of its intervals by one near each point of gradient catastrophe. This result justifies the formation and extinction of the multiphase solutions of the Whitham equations. Furthermore we characterize a class of initial data for which all the points of gradient catastrophe occur only a finite number of times and therefore the support of the Lax—Levermore minimizer consists of a finite number of disjoint intervals for any x and t 0. This corresponds to give an upper bound to the genus of the solution of the Whitham equations. Similar results are obtained for the semi-classical limit of the defocusing nonlinear Schrödinger equation.     

Particle image velocimetry experiments on a macro-scale model for bacterial flagellar bundling

Escherichia coli (E. coli) and other bacteria are propelled through water by several helical flagella, which are rotated by motors embedded at random points on the cell wall. Depending on the handedness and rotation sense, the motion of the flagella induces a flow field that causes them to wrap around each other and form a bundle. Our objective is to understand and model the mechanics of this process. Full-scale flagella are 10 m in length, 20 nm in diameter, and turn at a rate of 100 Hz. To accurately simulate bundling at a more easily observable scale, we built a scale model in which 20-cm-long helices are rotated in 100,000 cp silicone oil (Poly-di-methyl-siloxane). The highly viscous oil ensures an appropriately low Reynolds number. We developed a macro-scale particle image velocimetry (PIV) system to measure the full-field velocity distribution for rotating rigid helices and rotating flexible helices. In the latter case, the helices were made from epoxy-filled plastic tubing to give approximately the same ratio of elastic to viscous stresses as in the full-scale flagella. Comparison between PIV measurements and slender-body calculations shows good agreement for the case of rigid helices. For the flexible helices, we find that the flow field generated by a bundle in the steady state is well approximated by the flow generated by a single rigid helix with twice the filament radius.