FT-IR study on solvent effects in building blocks of bioactive compounds. V

3-Hydroxy-4-hydroxymethyl pyrrolidin-2-ones, easily prepared from the Baylis–Hillman adduct 1-ethyl-4-methyl-2-hydroxy-3-methylenebutanedioate, are useful intermediates in the synthesis of bioactive compounds. In order to understand the mechanism involved in this reaction, vibrational and Montecarlo molecular mechanics conformational analysis on 1-ethyl-4-methyl-2-hydroxy-3-methylenebutanedioate were carried out, confirming the existence of a low energy intramolecular H-bonded five-member ring.     

Small random perturbations of finite- and infinite-dimensional dynamical systems: Unpredictability of exit times

We apply previous results on the pathwise exponential loss of memory of the initial condition for stochastic differential equations with small diffusion to the problem of the asymptotic distribution of the first exit times from an attracted domain. We show under general hypotheses that the suitably rescaled exit time converges in the zero-noise limit to an exponential random variable. Then we extend the results to an infinite-dimensional case obtained by adding a small random perturbation to a nonlinear heat equation.     

Triorganotin 4-isopropylbenzoates as model transesterification catalysts for triorganotin carboxylates grafted to cross-linked polystyrene

Starting from 4-isopropylbenzoic acid, three new triorganotin carboxylates bearing methyl, butyl and phenyl substituents at tin, respectively, were prepared and fully characterized by spectroscopic and thermal techniques, with particular regard to the coordination number of tin atom, in solution as well as in the solid state. The triorganotin compounds, tested as transesterification catalysts in the reaction between ethyl acetate and primary, secondary or tertiary alcohol, respectively, displayed, as expected, a strong decrease of activity on passing from the primary to the tertiary alcohol reactant. Different activities by the tin carboxylates were also observed in the reaction between primary alcohol and ethyl acetate. The reaction mechanism, as elucidated by Sn NMR, involves coordination of both ester substrate and alcohol reactant to the triorganotin compound, the reaction conversion appearing related not only to the Lewis acidity of the tin atom, but also to the nature of the reactants. Preliminary catalytic tests were also carried out in the reaction between glyceryl tridodecanoate (as a model of natural triglyceride) and ethanol, mimicking the preparation of biodiesel fuel. Although in this case lower conversions were obtained with respect to the reactions on ethyl acetate, the catalytic activity of organotin derivatives appears considerable.     

PHEMA hydrogels obtained by a novel low-heat curing procedure with a potential for in situ preparation

In this work, we report on poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels obtained by a low heat curing reaction. These materials are suitable for in situ preparation and therefore endowed with a potential for several biomedical applications. The novel procedure adopted involves as the first step the synthesis of a soluble oligomeric PHEMA precursor containing polymerizable functions as side substituents. As the second step, the precursor is dissolved in equal amounts of 2-hydroxyethyl methacrylate (HEMA) and water, to form a viscous but still injectable syrup. A low temperature water soluble initiator is then added. The curing reaction starts promptly and is completed within few minutes. During the entire process the internal temperature never rises above 40 degrees C. Preliminary mechanical characterizations performed on the hydrogels in their water-swollen state and diffusion tests in absorption/desorption experiments clearly indicated that on all respects the novel hydrogels are comparable with conventional PHEMA hydrogels obtained according to literature from HEMA in the presence of divinyl crosslinkers. However, the much shorter curing time combined with the far lower curing temperature endow the new hydrogels with a higher potential in view of specific surgical requirements, and particularly for in situ preparation.     

Positive and negative ion chemistry of the anesthetic halothane (1-bromo-1-chloro-2,2,2-trifluoroethane) in air plasma at atmospheric pressure

The ion chemistry of 1-bromo-1-chloro-2,2,2-trifluoroethane (the common anesthetic halothane) in air plasma at atmospheric pressure was investigated by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The major positive ion observed at low declustering (API interface) energies is the ionized dimer, M(+.)M, an unexpectedly abundant species which possibly is stabilized by two H-bonding interactions. At higher energies [M--HF](+.) and [M--Br](+) prevail; the former, corresponding to ionized olefin [ClBrC=CF(2)](+.), appears to originate from M(+.)M and is quite stable towards fragmentation. The latter fragment ion ([M--Br](+)) and its analogue, [M--Cl](+), which is also observed though at much lower abundance, are originally ethyl cations (+)CHX--CF(3) (X = Br, Cl) which, upon collisional activation, rearrange and fragment to CHFX(+) via elimination of CF(2). All of the above described ions are also observed in humid air: in addition, the oxygenated ion [ClBrC=CFOH](+.) also forms in humid air via water addition to [ClBrC=CF(2)](+.) and HF elimination, as observed earlier for ionized trichloroethene. In contrast with similar chloro- and fluoro-substituted ethanes, halothane does not react with H(3)O(+) in the APCI plasma, a result confirmed by selected ion APCI triple-quadrupole (TQ) experiments. Major negative ions formed from halothane in the air plasma are Br(-) and, to a lesser extent, Cl(-), and their complexes with neutral halothane. APCI-TQ experiments indicated that Br(-) and Cl(-) are formed via reaction of halothane with O(2) (-.), O(2) (-.)(H(2)O) and O(3) (-.), possibly via dissociative electron transfer or nucleophilic substitution. Competing proton transfer was also observed in the reaction with O(2) (-.) and, at high halothane pressure, also with O(2) (-.)(H(2)O); at lower pressures the molecular anion M(-.) was observed instead. The other minor anions of the air plasma, NO(2) (-), N(2)O(2) (-.) and NO(3) (-), were found to be unreactive towards halothane.     

A fluorescent molecular imaging probe with selectivity for soluble tau aggregated protein

Soluble forms of aggregated tau misfolded protein, generally termed oligomers, are considered to be the most toxic species of the different assembly states that are the pathological components of neurodegenerative disorders. Therefore, a critical biomedical need exists for imaging probes that can identify and quantify them. We have designed and synthesized a novel fluorescent probe, pTP-TFE for which binding and selectivity profiles towards aggregated tau and Aβ proteins were assessed. Our results have shown pTP-TFE to be selective for early forms of soluble tau aggregates, with high affinity of dissociation constants (K_d) = 66 nM, and tenfold selectivity over mature tau fibrils. Furthermore, we found that pTP-TFE is selective for tau over Aβ aggregates and had good cell permeability. This selectivity of pTP-TFE towards early forms of aggregated tau protein ex vivo was also supported with studies on human brain tissue containing tau and Aβ pathology. To the best of our knowledge, this is the first fluorescent molecule to be reported to have this form of selectivity profile, which suggests that pTP-TFE is a unique probe candidate for imaging-based detection of early stages of Alzheimer''s disease and other tauopathies.

pTP-TFE imaging probe can distinguish soluble tau aggregated proteins from other aggregated proteins enabling earlier detection of neurodegenerative diseases.     

Relaxation processes of the liquid crystal ME6N in the isotropic phase studied by Raman scattering experiments

We have investigated the Raman profiles of the nu(C[Triple Bond]N) and nu(C=O) vibrational modes of the nematic liquid crystal ME6N (4-cyanophenyl-4(')-hexylbenzoate) in the isotropic phase at different temperatures and used them as probes of the dynamics and structural organization of this liquid. The vibrational time correlation functions of the nu(C[Triple Bond]N) mode, rather adequately interpreted within the assumption of exponential modulation function (the Kubo-Rothschild theory), indicate that the system experiences an intermediate dynamical regime that gets only slightly faster with increasing temperature. However, this theory fails in predicting the non-exponential behavior that the time correlation functions manifest in the long time range (t>3 ps). For this reason we have additionally approached the interpretation of vibrational correlation functions in terms of the theory formulated by Rothschild and co-workers for locally structured liquids. The application of this theory reveals that the molecular dynamics in this liquid crystal in the isotropic phase is that deriving from a distribution of differently sized clusters, which narrows as the temperature increases. Even at the highest temperature reached in this study (87 degrees C above the nematic-isotropic transition), the liquid has not yet achieved the structure of the simple liquid and the dynamics has not reached the limit of the single channel process. The vibrational and orientational relaxations occur in very different time scales. The temperature independence of the orientational dynamics in the whole range from 55 degrees C to 135 degrees C has been referred to the nonhydrodynamic behavior of the system, arising when local pseudonematic structures persist for times longer than the orientational relaxation. The occurrence of the process of resonant vibrational energy transfer between the C=O groups of adjacent molecules has been revealed in the isotropic phase by a slightly positive Raman noncoincidence effect in the band associated with the nu(C=O) mode. A qualitative interpretation is tentatively given in terms of partial cancellation of contributions deriving from structures having opposite orientations of their C=O groups.     

Investigation into the Use of Encorafenib to Develop Potential PROTACs Directed against BRAFV600E Protein

BRAF is a serine/threonine kinase frequently mutated in human cancers. BRAF^V600E mutated protein is targeted through the use of kinase inhibitors which are approved for the treatment of melanoma; however, their long-term efficacy is hampered by resistance mechanisms. The PROTAC-induced degradation of BRAF^V600E has been proposed as an alternative strategy to avoid the onset of resistance. In this study, we designed a series of compounds where the BRAF kinase inhibitor encorafenib was conjugated to pomalidomide through different linkers. The synthesized compounds maintained their ability to inhibit the kinase activity of mutated BRAF with IC₅₀ values in the 40–88 nM range. Selected compounds inhibited BRAF^V600E signaling and cellular proliferation of A375 and Colo205 tumor cell lines. Compounds 10 and 11, the most active of the series, were not able to induce degradation of mutated BRAF. Docking and molecular dynamic studies, conducted in comparison with the efficient BRAF degrader P5B, suggest that a different orientation of the linker bearing the pomalidomide substructure, together with a decreased mobility of the solvent-exposed part of the conjugates, could explain this behavior.     

Achillea moschata Wulfen: From Ethnobotany to Phytochemistry,Morphology, and Biological Activity

A multidisciplinary investigation on Achillea moschata Wulfen (Asteraceae) is outlined herein. This work, part of the European Interreg Italy–Switzerland B-ICE project, originated from an ethnobotanical survey performed in Chiesa in Valmalenco (Sondrio, Lombardy, Northern Italy) in 2019–2021 which highlighted this species’ relevance of use in folk medicine to treat gastrointestinal diseases. In addition, this contribution included analyses of the: (a) phytochemical profile of the aqueous and methanolic extracts of the dried flower heads using LC-MS/MS; (b) morpho-anatomy and histochemistry of the vegetative and reproductive organs through Light, Fluorescence, and Scanning Electron Microscopy; (c) biological activity of the aqueous extract concerning the antioxidant and anti-inflammatory potential through cell-based in vitro models. A total of 31 compounds (5 phenolic acids, 13 flavonols, and 13 flavones) were detected, 28 of which included in both extracts. Covering and secreting trichomes were observed: the biseriate 10-celled glandular trichomes prevailing on the inflorescences represented the main sites of synthesis of the polyphenols and flavonoids detected in the extracts, along with volatile terpenoids. Finally, significant antioxidant and anti-inflammatory activities of the aqueous extract were documented, even at very low concentrations; for the first time, the in vitro tests allowed us to formulate hypotheses about the mechanism of action. This work brings an element of novelty due to the faithful reproduction of the traditional aqueous preparation and the combination of phytochemical and micromorphological research approaches.     

Concentration-dependent frequency shifts and Raman spectroscopic noncoincidence effect of the C=O stretching mode in dipolar mixtures of acetone/dimethyl sulfoxide. Experimental, theoretical, and simulation results

The nu(C=O) Raman band frequencies of acetone have been analyzed to separate the contributions of the environmental effect and the vibrational coupling to the gas-to-liquid frequency shifts of this band and to elucidate the changes in these two contributions upon dilution in DMSO. We have measured the frequencies of the nu((12)C=O) band in acetone/DMSO binary mixtures, the nu((13)C=O) band of the acetone-(13)C=O present as a natural abundance isotopic impurity in these mixtures, and both the nu((12)C=O) and nu((13)C=O) bands in the acetone-(12)C=O/acetone-(13)C=O isotopic mixtures at infinite dilution. These frequencies are compared with those of the nu((12)C=O) band in the acetone/CCl(4) binary mixtures measured previously. We have found the following three points: (i) The negative environmental contribution for the nu((12)C=O) oscillator of acetone completely surrounded by DMSO is reduced in magnitude by +5.5 cm(-1) and +7.8 cm(-1) upon the complete substitution of DMSO with acetone and CCl(4) molecules, respectively, indicating the progressive reduction of the attractive forces exerted by the environment on the nu((12)C=O) mode of acetone. (ii) In DMSO and other solvents, the contribution of the vibrational coupling to the frequency of the isotropic Raman nu((12)C=O) band of acetone becomes progressively more negative with increasing acetone concentration up to a value of -5.5 cm(-1), while the contribution to the frequency of the anisotropic Raman band remains approximately unchanged. The only difference resides in the curvatures of the concentration dependencies of these contributions which depend on the relative solute/solvent polarity. (iii) The noncoincidence effect (separation between the anisotropic and isotropic Raman band frequencies) of the nu(C=O) mode in the acetone/DMSO mixtures exhibits a downward (concave) curvature, in contrast to that in the acetone/CCl(4) mixtures, which shows an upward (convex) curvature. This result is supported by MD simulations and by theoretical predictions and is interpreted as arising from the reduction and enhancement of the short-range orientational order of acetone in the acetone/DMSO and acetone/CCl(4) mixtures, respectively.