Postprandial C-Peptide to Glucose Ratio as a Marker of β Cell Function: Implication for the Management of Type 2 Diabetes

C-peptide is secreted from pancreatic β cells at an equimolar ratio to insulin. Since, in contrast to insulin, C-peptide is not extracted by the liver and other organs, C-peptide reflects endogenous insulin secretion more accurately than insulin. C-peptide is therefore used as a marker of β cell function. C-peptide has been mainly used to assess the presence of an insulin-dependent state for the diagnosis of type 1 diabetes. However, recent studies have revealed that β cell dysfunction is also a core deficit of type 2 diabetes, and residual β cell function is a key factor in achieving optimal glycemic control in patients with type 2 diabetes. This review summarizes the role of C-peptide, especially the postprandial C-peptide to glucose ratio which likely better reflects maximum β cell secretory capacity compared with the fasting ratio in assessing β cell function, and discusses perspectives on its clinical utility for managing glycemic control in patients with type 2 diabetes.     

Synthesis of Multiwalled Carbon Nanotubes–Poly(Methacrylic Acid) Nanohybrid Systems: Characterization,Thermal Properties,and In Vitro Release Studies of Naproxen as a Model Drug

Nanohybrid systems based on carbon nanotubes and pH-sensitive poly(methacrylic acid) were prepared through attaching polymer chains onto carbon nanotubes. First, polymerizable groups were attached onto carbon nanotube walls, then the polymerizable groups were copolymerized with different ratios of methacrylic acid. Obtained systems were studied and characterized through Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. A model drug (naproxen) was entrapped into the prepared materials and in vitro release studies were performed in pH 1 (simulated gastric fluids) and pH 7.4 (simulated intestinal fluids). It was noticed that release in simulated intestinal fluids was faster than simulated gastric fluids, therefore the prepared nanohybrid systems can be considered as appropriate carriers for colon-specific drug delivery.     

The polyfluorenes: a family of versatile electroactive polymers—III. Poly(9,9-dimethylfluorene) as an electrode modifier in the study of some systems known to be reversible on platinum

The poly(9,9-dimethylfluorene), an electroactive polymer reversibly n- or p-doped, is used as a metallic electrode modifier for the reduction or the oxidation of various substrates known to give reversible systems in more classical conditions. Such a study points out that this polymer can be used as anode or cathode within a very large potential range of 4.5 V. Different modes of charge transfer processes are proposed as a function of different substrates.     

Nitrogen donor-controlled chemoselectivity of reaction in oxidation of sulfides with tetra-n-butylammonium hydrogen monopersulfate catalyzed by a partially β-brominated meso-tetraphenylporphyrinatomanganese(III) acetate: a clue to the nature of active oxidant

Highly efficient and rapid oxidation of different sulfides to the corresponding sulfones with tetra-n- butylammonium hydrogen monopersulfate (TBAO) in the presence of catalytic amounts of Mn(TPPBr₂)OAc at room temperature is reported. Contrary to other nitrogen donors, using 4-cyanopyridine as co-catalyst leads to an increase in the ratio of sulfoxide to sulfone in the products. Comparison of the chemoselectivity of reaction in the presence of different nitrogen donors as co-catalyst shows the involvement of a high-valent Mn-oxo species as well as the six-coordinate Mn(TPPBr₂)(HSO₅)(B) (B = nitrogen donors) complex in sulfide oxidation reactions with TBAO.     

Comment on: “Experimental and Theoretical Investigations of Tetrakis (Thiourea) Palladium Chloride Semi-Organic Non-Linear Optical Crystal: An Approach to NLO Application” [(2018) Silicon 10 (3):841–850]

Silicon - In a recent paper [(2018) Silicon 10 (3):841–850] Rajagopalan et al. studied the physical properties of the Tetrakis (Thiourea) Palladium Chloride Semi-Organic Non-Linear Optical...     

Liquid crystalline polymers VIII: thermotropic liquid crystalline poly(hydrazone–ether)s containing bis-thiophene linked to the main chain through spacers of various lengths

A new series of poly(hydrazone–ether)s was synthesized from 3,4-dimethylthieno [2,3-b] thiophene-2, 5-dicarbohydrazide, II and 4,4′-diformyl-α, ω-diphenoxyalkanes or 4,4′-diformyl -2,2′-dimethoxy -α, ω-diphenoxyalkanes. The inherent viscosities of the polymers were in the range 0.22 – 0.56 dIg^?1. Majority of the polymers were soluble in concentrated H₂SO₄. Their thermotropic liquid crystalline properties were examined by DSC, an optical polarizing microscopy using a hot stage and thermogravimetric analyses. The polymers exhibited almost thermotropic liquid crystalline properties. In most cases, the mesophases extended up to 430°C, where thermal decomposition prevented further observation.

β-cyclodextrin as a Partial Replacement of Phosphorus Flame Retardant for Poly(Lactic Acid)/Poly(Methyl Methacrylate): A More Environmental Friendly Flame-Retarded Blends

β-Cyclodextrin was used together with isopropylated triaryl phosphate ester flame retardant to improve the flame resistance of poly(lactic acid)/poly(methyl methacrylate). Poly(lactic acid)/poly(methyl methacrylate)/flame-retardant blend (with and without β-cyclodextrin) was evaluated using limiting oxygen index, Underwriters Laboratories-94 vertical burning test, scanning electron microscopy, and thermogravimetric analysis (in O₂ and N₂). The addition of β-cyclodextrin was able to reduce the amount of flame retardant required for poly(lactic acid)/poly(methyl methacrylate) blends to achieve self-extinguishing properties. The poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends achieved Underwriters Laboratories-94, V-0, and limiting oxygen index value of 29.3%. A compact and wide coverage of char layer was formed on the burning surface of poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends.     

[Ph4P][CrO3(OH)] – a wonder molecule: its behaviour as a bifunctional autocatalyst in water-splitting for the perpetual generation of dihydrogen and a catalyst mimicking catalase function

An oxygen-rich chromium (VI) complex, Ph₄P[CrO₃(OH)], reduces water present in non-aqueous media, viz, acetonitrile or dichloromethane to dihydrogen fuel autocatalytically, while oxidising functionalized organic substrates. The same catalyst also shows a catalase like activity on H₂O₂ also in non-aqueous media.     

Direct syngas to DME as a clean fuel: The beneficial use of ultrasound for the preparation of CuO–ZnO–Al2O3/HZSM-5 nanocatalyst

A series of CuO–ZnO–Al₂O₃/HZSM-5 nanocatalysts prepared by impregnation, co-precipitation–physically mixing and combined co-precipitation–ultrasound methods and their catalytic activity investigated toward direct conversion of syngas to DME. BET, XRD, FESEM, TPR-H₂ and FTIR techniques were used to characterize nanocatalysts. XRD and FTIR results showed that structure of HZSM-5 is not damaged even after it is loaded with CuO–ZnO–Al₂O₃ nanoparticles. TPR-H₂ profiles indicated that reducibility of co-precipitation–ultrasound nanocatalyst is higher than other catalysts. It is found that employing ultrasound energy has great influence on the dispersion of nanocatalyst and its catalytic performance. Size distribution histogram of this nanocatalyst indicated that active phase particle size is between 25.7 and 125.4 nm and their average size is 47.86 nm. The physically mixing of CuO–ZnO–Al₂O₃ and HZSM-5 resulted in the low catalytic activity, indicating that the closest packing of both active sites for CO hydrogenation and methanol dehydration is necessary for direct synthesis of DME. The nanocatalyst loses negligible activity over the course of reaction due to coke formation on copper species.     

ω-Iodinated poly(dimethylsiloxane) as a chain transfer agent in iodine transfer radical polymerization of vinyl acetate and dibutyl maleate: synthesis and structural characterization

Iodine transfer radical homo- (ITP) and copolymerization (ITCP) of vinyl acetate (VAc) with dibutyl maleate (DBM) initiated by 2,2?-azobis(isobutyronitrile) (AIBN) were performed in bulk at 80 °C in the presence of ω-iodo- terminated poly(dimethylsiloxane) (PDMS-I) as a macro-chain transfer agent (macro-CTA). ¹H-NMR and gel permeation chromatography (GPC) results confirmed formation of the PDMS-b-PVAc diblock copolymer. Moreover, the results of ¹H-NMR showed that the iodo-terminated chain ends are unstable and decompose to the aldehyde moieties. On the other hand, different behaviour was observed in the ITCP of the VAc and DBM. ¹H-NMR and GPC results showed that presence of DBM in the reaction medium leads to degradation of the C-I bond of the PDMS-I, resulting in the generation of HI. In fact, PDMS-I acts as in situ generator of the CTA in the presence of DBM via reaction between the generated HI and VAc. In other words, it was found that P(VAc-co-DBM) copolymer chains are synthesised by ITP mechanism in the presence of in situ generated 1-iodoethyl acetate as a CTA. Therefore, a mixture of PDMS and P(VAc-co-DBM) chains was obtained.     

Transformation of β-damascone to (+)-(S)-4-hydroxy-β-damascone by fungal strains and its evaluation as a potential insecticide against aphids Myzus persicae and lesser mealworm Alphitobius diaperinus Panzer

Microbial conversion of β-damascone (1) into 4-hydroxy-β-damascone (2) was studied. The results showed the potential of the tested biocatalysts for the regio- and enantioselective hydroxylation of substrate 1. The highest enantioselectivity was exhibited by strain Mortierella isabellina AM212. β-Damascone (1) was a relatively good deterrent towards Alphitobius diaperinus and it was behaviorally inactive to Myzus persicae. The racemic compound 2 and its (+)-(S)-enantiomer were stronger antifeedants against A. diaperinus than β-damascone (1), in the case of M. persicae only (+)-(S)-(2) exhibited the deterrent properties.     

Synthesis of a New Interpenetrated Mixed Ligand Ni(II) Metal–Organic Framework: Structural, Thermal and Fluorescence Studies and its Thermal Decomposition to NiO Nanoparticles

Reaction of terephthalic acid and pyrazine with nickel nitrate under hydrothermal conditions forms a 3D metal–organic framework with the composition of [Ni(μ₃ ? tp)(μ₂ ? pyz)]_n (1), where H₂tp = 1,4-benzenedicarboxylic acid (terephthalic acid) and pyz = pyrazine. X-ray single crystal analysis reveals that Ni(II) centers adopt a distorted octahedral geometry which are surrounded by four oxygen atoms from three tp groups and two nitrogen atoms of pyrazine molecules in equatorial and axial positions, respectively. Coordination of Ni(II) centers by terephthalate linkers in ac plane forms infinite (4, 4)-connected 2D layers, which are further joined together by pyrazine groups to form an interlocked 3D structure. Topological studies show a two-fold interpenetrated uninodal 3D network with point symbol of (4¹²·6³). The polymer shows a blue emission band at 467 nm in the solid state at room temperature. The X-ray power diffractions (PXRD) and thermal gravimetric analysis of 1 are also presented and discussed. NiO nanoparticles have been prepared via direct calcination of 1 at 600 °C, with sizes of about 35–45 nm. Nanoparticles were further characterized by IR, scanning electron microscopy equipped with energy dispersive X-ray analyses and PXRD technique.     

Isomerism as a remarkable tool for the design of new potentially bridging macrocycle ligands: Synthesis and characterization of the [Cu(4-L1)](NO3)2·2H2O polymeric chain (4-L1=mono-N (4-picolyl)cyclen)

A new coordination complex [Cu(4-L1)](NO₃)₂·2H₂O (1) based on the functionalized cyclen mono-N (4-picolyl)cyclen (4-L1) has been prepared and characterized by X-ray diffraction. The structure of 1 can be described as a monodimensional coordination polymer in which the macrocycle ligand acts as bridging ligand. Examination of the inter-chain distances revealed the presence of hydrogen bonds between oxygen atoms of the nitrate anions and the hydrogen atoms of two secondary amines of the macrocycle ligands, affording isolated “double-chain” units. The overall structure of 1 consists of alternating succession of cationic layers of infinite “double-chain” units and anionic nitrate-water H-bonded layers.