Enantioselective Approach for Expanding the Three-Dimensional Space of Tetrahydroquinoline to Develop BET Bromodomain Inhibitors**

The pharmaceutical industry has a pervasive need for chiral specific molecules with optimal affinity for their biological targets. However, the mass production of such compounds is currently limited by conventional chemical routes, that are costly and have an environmental impact. Here, we propose an easy access to obtain new tetrahydroquinolines, a motif found in many bioactive compounds, that is rapid and cost effective. Starting from simple raw materials, the procedure uses a proline-catalyzed Mannich reaction followed by the addition of BF₃ ⋅ OEt₂, which generates a highly electrophilic aza-ortho-quinone methide intermediate capable of reacting with different nucleophiles to form the diversely functionalized tetrahydroquinoline. Moreover, this enantioselective one-pot process provides access for the first time to tetrahydroquinolines with a cis-2,3 and trans-3,4 configuration. As proof of concept, we demonstrate that a three-step reaction sequence, from simple and inexpensive starting compounds and catalysts, can generate a BD2-selective BET bromodomain inhibitor with anti-inflammatory effect.     

Determination of L-tryptophan-serum albumin binding by high-performance liquid chromatography

Summary Two high-performance liquid chromatography (HPLC) techniques were developed for the determination of binding constants in the interaction of serum albumin with L-tryptophan: internal calibration and external calibration. The results obtained were compared with those obtained by the classical method of equilibrium dialysis and by gel filtration. While all the methods are equally reliable, the internal and external calibration techniques seem to be superior in their simplicity, speed and convenience.     

Langmuir — Blodgett deposition of lipid films on hydrogel as a basis for biosensor development

Lipid membranes composed of phosphatidyl choline and cholesterol were interfaced to polyacrylamine hydrogen by Langmuir—Blodgett thin-film deposition. The extent of lipid adsorption to the gel surface was critically dependent on the hydration of the polymer as determined by contact angle measurements. Some electrochemical transducers incorporating the deposited membrane/gel structure responded positively to phloretin and valinomycin. Limitations to the construction of this device are discussed.     

Ratiometric Detection of microRNA Using Hybridization Chain Reaction and Fluorogenic Silver Nanoclusters

miRNA (miR)-155 is a potential biomarker for breast cancers. We aimed at developing a nanosensor for miR-155 detection by integrating hybridization chain reaction (HCR) and silver nanoclusters (AgNCs). HCR serves as an enzyme-free and isothermal amplification method, whereas AgNCs provide a built-in fluorogenic detection probe that could simplify the downstream analysis. The two components were integrated by adding a nucleation sequence of AgNCs to the hairpin of HCR. The working principle was based on the influence of microenvironment towards the hosted AgNCs, whereby unfolding of hairpin upon HCR has manipulated the distance between the hosted AgNCs and cytosine-rich toehold region of hairpin. As such, the dominant emission of AgNCs changed from red to yellow in the absence and presence of miR-155, enabling a ratiometric measurement of miR with high sensitivity. The limit of detection (LOD) of our HCR-AgNCs nanosensor is 1.13 fM in buffered solution. We have also tested the assay in diluted serum samples, with comparable LOD of 1.58 fM obtained. This shows the great promise of our HCR-AgNCs nanosensor for clinical application.     

Vitamin A and Bone Health: A Review on Current Evidence

Vitamin A is a fat-soluble micronutrient essential for growth, immunity, and good vision. The preformed retinol is commonly found in food of animal origin whereas provitamin A is derived from food of plant origin. This review summarises the current evidence from animal, human and cell-culture studies on the effects of vitamin A towards bone health. Animal studies showed that the negative effects of retinol on the skeleton were observed at higher concentrations, especially on the cortical bone. In humans, the direct relationship between vitamin A and poor bone health was more pronounced in individuals with obesity or vitamin D deficiency. Mechanistically, vitamin A differentially influenced the stages of osteogenesis by enhancing early osteoblastic differentiation and inhibiting bone mineralisation via retinoic acid receptor (RAR) signalling and modulation of osteocyte/osteoblast-related bone peptides. However, adequate vitamin A intake through food or supplements was shown to maintain healthy bones. Meanwhile, provitamin A (carotene and β-cryptoxanthin) may also protect bone. In vitro evidence showed that carotene and β-cryptoxanthin may serve as precursors for retinoids, specifically all-trans-retinoic acid, which serve as ligand for RARs to promote osteogenesis and suppressed nuclear factor-kappa B activation to inhibit the differentiation and maturation of osteoclasts. In conclusion, we suggest that both vitamin A and provitamin A may be potential bone-protecting agents, and more studies are warranted to support this hypothesis.     

Design,Synthesis, and Biochemical Evaluation of Alpha-Amanitin Derivatives Containing Analogs of the trans-Hydroxyproline Residue for Potential Use in Antibody-Drug Conjugates

Alpha-amanitin, an extremely toxic bicyclic octapeptide extracted from the death-cap mushroom, Amanita phalloides, is a highly selective allosteric inhibitor of RNA polymerase II. Following on growing interest in using this toxin as a payload in antibody-drug conjugates, herein we report the synthesis and biochemical evaluation of several new derivatives of this toxin to probe the role of the trans-hydroxyproline (Hyp), which is known to be critical for toxicity. This structure activity relationship (SAR) study represents the first of its kind to use various Hyp-analogs to alter the conformational and H-bonding properties of Hyp in amanitin.     

Membrane introduction mass spectrometry

An overview of membrane introduction mass spectrometry (MIMS) is presented and comparisons are made with other direct sample introduction techniques. Special attention is given to the unique advantages and the limitations of newer variants on the MIMS technique, including affinity MIMS, reverse-phase and trap MIMS. The salient features of the interfaces used in MIMS are summarized and the various membrane materials commonly used are delineated. The applicability of MIMS is illustrated via discussion of

1. (i) bioreactor monitoring (represented by yeast fermentation),

2. (ii) environmental monitoring (illustrated by analysis of contaminated ground water samples) and

3. (iii) on-line chemical reaction monitoring (exemplified by the photolysis of aryl esters).

The applicability of MIMS to the analysis of environmental samples, including complex mixtures in water, air and soil, is noted.     

Thermal diffusivity of polymer films by pulsed photothermal radiometry

We have developed a pulsed photothermal radiometry technique for determining the thermal diffusivity parallel to the surface of a polymer film that involves flashing a line-shaped laser beam on the surface of the sample at right angle to its length, and monitoring the temperature change with time at a distance from the line source using an infrared detector. Combining this with our previous laser-flash radiometry method for thermal diffusivity measurement perpendicular to the film surface, we can now measure the thermal diffusivity of a polymer film along all directions. These two techniques have been used to study uniaxially and biaxially oriented poly(ethylene terephalate) and uniaxially drawn ultrahigh molecular weight polyethylene films. For uniaxially oriented poly(ethylene terephalate), the thermal diffusivity along the draw direction is substantially higher than that in the transverse direction, which in turn, is slightly higher than that in the thickness direction. For a polyethylene film with a draw ratio of 200, the axial thermal diffusivity is extremely high, being about five times that of stainless steel. The anisotropy of the thermal diffusivity of this film exceeds 90. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1621–1631, 1997     

Surface functionalization of polymer latex particles. II. Catalytic oxidation of poly(methylstyrene) latexes in the presence of cetyltrimethylammonium bromide

Surface-functionalized cationic poly(methylstyrene) (PMS) latex particles containing aldehyde and carboxylic acid groups were successfully achieved via an emulsion polymerization of 3(4)-methylstyrene in the presence of cetyltrimethylammonium bromide, followed by an in-situ oxidation catalyzed by copper chloride and tert-butyl hydroperoxide (t-BuOOH). Factors such as the type of metal catalyst, oxidant, and their concentration strongly affected the rate of oxidation. Step addition of t-BuOOH resulted in both a higher degree of oxidation and a more uniform distribution of particle size of the functionalized PMS as compared to the batch addition method. The effect of organic solvent was found to be insignificant, and the oxidation could still proceed in its absence. The particle sizes increased significantly during the oxidation but could be controlled by using crosslinked PMS latexes. Finally, the versatility of this oxidation process was demonstrated by oxidation of the polymer with a solid loading as high as 28%. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3585–3593, 1997     

Automated discovery of noncovalent inhibitors of SARS-CoV-2 main protease by consensus Deep Docking of 40 billion small molecules

Recent explosive growth of ‘make-on-demand’ chemical libraries brought unprecedented opportunities but also significant challenges to the field of computer-aided drug discovery. To address this expansion of the accessible chemical universe, molecular docking needs to accurately rank billions of chemical structures, calling for the development of automated hit-selecting protocols to minimize human intervention and error. Herein, we report the development of an artificial intelligence-driven virtual screening pipeline that utilizes Deep Docking with Autodock GPU, Glide SP, FRED, ICM and QuickVina2 programs to screen 40 billion molecules against SARS-CoV-2 main protease (Mpro). This campaign returned a significant number of experimentally confirmed inhibitors of Mpro enzyme, and also enabled to benchmark the performance of twenty-eight hit-selecting strategies of various degrees of stringency and automation. These findings provide new starting scaffolds for hit-to-lead optimization campaigns against Mpro and encourage the development of fully automated end-to-end drug discovery protocols integrating machine learning and human expertise.

Deep learning-accelerated docking coupled with computational hit selection strategies enable the identification of inhibitors for the SARS-CoV-2 main protease from a chemical library of 40 billion small molecules.