Determination of the 15N chemical shift anisotropy in natural abundance samples by proton-detected 3D solid-state NMR under ultrafast MAS of 70 kHz

Chemical shift anisotropy (CSA) is a sensitive probe of electronic environment at a nucleus, and thus, it offers deeper insights into detailed structural and dynamic properties of different systems, for example, chemical, biological, and materials. Over the years, massive efforts have been made to develop recoupling methods that reintroduce CSA interaction under magic angle spinning (MAS) conditions. Most of them require slow or moderate MAS (≤20 kHz) and isotopically enriched samples. On the other hand, to the best of the authors' knowledge, no ¹³C or ¹⁵N CSA recoupling schemes at ultrafast MAS (≥60 kHz) suitable for cost-effective natural abundant samples have been developed. We present here a proton-detected 3D ¹⁵N CS/¹⁵N CSA/¹H CS correlation experiment which employs ¹H indirect detection for sensitivity enhancement and a γ-encoded -symmetry-based CSA recoupling scheme. In particular, two different symmetries, that is, R8³₇ and R10⁴₉, are first tested, in a 2D ¹⁵N CSA/¹H CS version, on [U-¹⁵N]-L-histidine·HCl·H₂O as a model sample under 70 kHz MAS. Then the 3D experiment is applied on glycyl-L-alanine at natural abundance, resulting in site-resolved ¹⁵N CSA lineshapes from which CSA parameters are retrieved by SIMPSON numerical fittings. We demonstrate that this 3D R-symmetry-based pulse sequence is highly robust with respect to wide-range offset mismatches and weakly dependent to rf inhomogeneity within mis-sets of ±10% from the theoretical value.     

Analytical approach to relaxation dynamics of condensed Bose gases

The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes.     

Self-Propagated para-Fluoro-Thiol Reaction

We introduce a protecting-group-free concept for the powerful para-fluoro-thiol reaction (PFTR) employing a source of fluoride ions as base. The reaction is shown to be self-propagating, with under-stoichiometric amounts of base, thus effectively foregoing the need for high base concentrations. Careful tuning of the solvent–thiol combination allows for quantitative conversion, in some cases within a short timeframe, when only minimal amounts of base are used, allowing the PFTR reaction to essentially proceed base-free.     

On the stochastic vehicle routing problem with time windows,correlated travel times,and time dependency

4OR - Most state-of-the-art algorithms for the Vehicle Routing Problem, such as Branch-and-Price algorithms or meta heuristics, rely on a fast feasibility test for a given route. We devise the...     

Development of easy‐to‐use reverse‐phase liquid chromatographic methods for determining PRE‐084, RC‐33 and RC‐34 in biological matrices. The first step for in vivo analysis of sigma1 receptor agonists

Over the years there has been a growing interest in the therapeutic potential for central nervous system pathologies of sigma receptor modulators. The widely studied PRE‐084 and our compounds RC‐33 and RC‐34 are very potent and selective sigma 1 receptor agonists that could represent promising drug candidates for Amyotrophic Lateral Sclerosis (ALS). Herein, we develop and validate robust and easy‐to‐use reverse‐phase chromatographic methods suitable for detecting and quantifying PRE‐084, RC‐33 and RC‐34 in mouse blood, brain and spinal cord. An HPLC/UV/ESI‐MS system was employed for analyzing PRE‐084 and an HPLC/UV‐PDA system for determining RC‐33 and RC‐34. Chromatographic separations were achieved on Waters Symmetry RP₁₈ column (150 × 3.9 mm, 5 µm), eluting with water and acetonitrile (both containing 0.1% formic acid) in gradient conditions. The recovery of PRE‐084, RC‐33 and RC‐34 was >95% in all the considered matrices. Their limits of quantitation and detection were also determined. Validation proved the methods be suitable for separating tested compounds from endogenous interferences, being characterized by good sensitivity, linearity, precision and accuracy. A preliminary central nervous system distribution study showed a high distribution of RC‐33 in brain and spinal cord, with concentration values well above the determined limit of quantitation. The proposed methods will be used in future preclinical investigations. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of 2-[(E)-Hex-1′-enyl]tetrahydropyran Starting from 3-Nitro-4,5-dihydro-6H-pyran

The four steps preparation of 2-[(E)-hex-1′-enyl]tetrahydropyran starting from 3-nitro-4,5-dihydro-6H-pyran has been carried out in 40% overall yield.     

Recombinant clotting factor VIII concentrates: Heterogeneity and high‐purity evaluation

Factor VIII is an important glycoprotein involved in hemostasis. Insertion of expression vectors containing either the full‐length cDNA sequence of human factor VIII (FLrFVIII) or B‐domain deleted (BDDrFVIII) into mammalian cell lines results in the production of recombinant factor VIII (rFVIII) for therapeutic usage. Three commercially available rFVIII concentrates (Advate^®, Helixate NexGen^® and Refacto^®), either FLrFVIII or BDDrFVIII, were investigated by 1‐ and 2‐DE and MS. The objective of this study was to compare the heterogeneity and the high purity of both rFVIII preparations before and after thrombin digestion. In particular, the 2‐D gel was optimized to better highlight the presence of contaminants and many unexpected proteins. Recombinant strategies consisting of insertion of expression vectors containing BDDrFVIII and FLrFVIII resulted in homogeneous and heterogeneous protein products, respectively, the latter consisting in a heterogeneous mixture of various B‐domain‐truncated forms of the molecule. Thrombin digestion of all the three rFVIII gave similar final products, plus one unexpected fragment of A2 domain missing 11 amino acids. Regarding the contaminants, Helixate NexGen^® showed the presence of impurities, such as Hsp70 kDa, haptoglobin and proapolipoprotein; Refacto^® showed glutathione S‐transferase and β‐lactamase, whereas Advate^® apparently did not contain any contaminants. The proteomic approach will contribute to improving the quality assurance and manufacturing processes of rFVIII concentrates. In this view, the 2‐DE is mandatory for revealing the presence of contaminants.     

Enantioselective Cytotoxicity of Chiral Diphosphine Ruthenium(II) Complexes Against Cancer Cells

The chiral cationic complex [Ru(η¹-OAc)(CO)((R,R)-Skewphos)(phen)]OAc ( 2 ^R ), isolated from reaction of [Ru(η¹-OAc)(η²-OAc)(R,R)-Skewphos)(CO)] ( 1 ^R ) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X=Y=OPiv 3 ^R ; X=SAc, Y=OAc 4 ^R ). The corresponding enantiomers 2 ^S - 4 ^S have been obtained from 1 ^S containing (S,S)-Skewphos. Reaction of 2 ^R and 2 ^S with (S)-cysteine and NaPF₆ at pH=9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF₆ (PP=(R,R)-Skewphos 2 ^R -Cys; (S,S)-Skewphos 2 ^S -Cys). The DFT energetic profile for 2 ^R with (S)-cysteine in H₂O indicates that aquo and hydroxo species are involved in formation of 2 ^R -Cys. The stability of the ruthenium complexes in 0.9 % w/v NaCl solution, PBS and complete DMEM medium, as well as their n-octanol/water partition coefficient (logP), have been evaluated. The chiral complexes show high cytotoxic activity against SW1736, 8505 C, HCT-116 and A549 cell lines with EC₅₀ values of 2.8–0.04 μM. The (R,R)-Skewphos derivatives show higher cytotoxicity compared to their enantiomers, 4 ^R (EC₅₀=0.04 μM) being 14 times more cytotoxic than 4 ^S against the anaplastic thyroid cancer 8505 C cell line.