Zirconocene-based catalysts for the ethylene-styrene copolymerization: reactivity ratios and reaction mechanism

A kinetic study of the ethylene-styrene copolymerization in the presence of rac-(ethylenebis- (1-indenyl)zirconium dichloride activated by MAO shows the peculiar behavior of this catalytic system that is known to produce crystalline nearly alternating copolymers. Some inferences on the monomer- metal interactions are made on the basis of this study. The parallel investigation on the catalyst based on isopropylidene(1-cyclopentadienyl)(9-fluorenyl)zirconium dichloride allows us to produce a stereoregular nearlyalternatingethylene-styrenecopolymeralsowiththiscatalyticsystem. Thesamemaintacticity seems to characterize the copolymers obtained with the C2 and Cs symmetric catalysts in accordance with the generally accepted mechanism of stereocontrol in the 1-alkene polymerizations

Influence of sociocultural factors on the ovulatory status of polycystic ovary syndrome.

OBJECTIVE: To evaluate the role of social and cultural differences inside the same ethnic group on the ovulatory status of women with polycystic ovary syndrome (PCOS). DESIGN: To correlate social and cultural status with the phenotypic expression (body weight and ovulation) and with androgen and insulin levels of PCOS. SETTING: University department of medicine. PATIENT(S): Two hundred and forty-four consecutive PCOS women. INTERVENTION(S): All studied patients completed a simple questionnaire to indicate their mean family income and their school education. MAIN OUTCOME MEASURE(S): Ovulation was assessed by measurement of serum progesterone on day 22 of a spontaneous or induced menstrual cycle. Levels of blood testosterone, sex hormone-binding globulin, insulin, and blood glucose were evaluated. RESULT(S): In the low to medium income group, 21% of patients had ovulatory PCOS, but the prevalence of the same PCOS phenotype was 43% in patients with high income. In patients with low education, only 12% presented with ovulatory PCOS compared with 47% of the patients with high education status. Mean family income negatively correlated with body mass index, waist circumference, insulin, and insulin resistance. Serum progesterone correlated negatively with insulin and insulin resistance. CONCLUSION(S): In an ethnically homogeneous PCOS population, high socioeconomic status was associated with a higher prevalence of the ovulatory phenotype. Differences in ovulatory status between the social classes seem to be related to differences in insulin levels and fat quantity and distribution

Layered double hydroxides with low Al content and new intercalate structures

Layered double hydroxides (LDHs) containing Mg2+ and Al3+ as divalent and trivalent cations, respectively, have been synthesized by a procedure based on hydrolysis of a mixture of metal alcoholates, and have been characterized mainly by Wide Angle X-ray diffraction (WAXD) and Fourier Transform Infrared (FTIR) measurements. The used procedure is suitable to prepare LDHs with Al molar fractions, x(Al)=Al/(Al+Mg), as low as 0.1. The same LDH preparation procedure, for x(Al)<0.1, produces thermally stable intercalates with alkoxy anions, exhibiting layers similar to those of brucite, which maintain a high degree of order only in the hexagonal packing of the hydroxide groups. In particular, the basal periodicity increases from nearly 0.8 nm up to nearly 1.3 nm, due to the parallel staking of hexanolate groups in the clay galleries. (C) 2012 Elsevier B.V. All rights reserved

Recent Advances in N-Heterocyclic Carbene Coinage Metal Complexes in A3-Coupling and Carboxylation Reaction

Owing of their accessibility and wide range of reactivities, alkynes make for fascinating building blocks. Either a selective alkyne carbon-carbon triple bond reaction or activation of the terminal alkyne C-H bond may be employed to functionalize them. Monocationic coinage metal complexes with a d10 electronic configuration are effective catalysts for alkyne activation. Silver(I) and gold(I) N-heterocyclic (NHC) systems are emerging as promising catalysts in multicomponent alkyne activation reactions; this review paper focuses on A3 (aldehyde-amine-alkyne)-coupling reaction and carbon dioxide fixation, furnishing a systematic overview of the scientific advances achieved during the last two decades. This study will carefully compare the corresponding silver and gold complexes employed in the two processes. The differences in reaction routes brought about by the catalyst ligand structure will be investigated with an emphasis on evaluating the benefits provided by the easily tuneable NHC backbone, in terms of chemo- and stereo-selectivit

Electrospun Membranes Designed for Burst Release of New Gold-Complexes Inducing Apoptosis of Melanoma Cells

Two non-commercial metallic Au-based complexes were tested against one of the most aggressive malignant melanomas of the skin (MeWo cells), through cell viability and time-lapse live-cell imaging system assays. The tests with the complexes were carried out both in the form of free metallic complexes, directly in contact with the MeWo cell line culture, and embedded in fibers of Polycaprolactone (PCL) membranes produced by the electrospinning technique. Membranes functionalized with complexes were prepared to evaluate the efficiency of the membranes against the melanoma cells and therefore their feasibility in the application as an antitumoral patch for topical use. Both series of tests highlighted a very effective antitumoral activity, manifesting a very relevant cell viability inhibition after both 24 h and 48 h. In the case of the AuM1 complex at the concentration of 20 mM, melanoma cells completely died in this short period of time. A mortality of around 70% was detected from the tests performed using the membranes functionalized with AuM1 complex at a very low concentration (3 wt.%), even after 24 h of the contact period. The synthesized complexes also manifest high selectivity with respect to the MeWo cells. The peculiar structural and morphological organization of the nanofibers constituting the membranes allows for a very effective antitumoral activity in the first 3 h of treatment. Experimental points of the release profiles were perfectly fitted with theoretical curves, which easily allow interpretation of the kinetic phenomena occurring in the release of the synthesized complexes in the chosen medium

Hydroamination of alkynes catalyzed by NHC-Gold(I) complexes: the non-monotonic effect of substituted arylamines on the catalyst activity

: Imines are valuable key compounds for synthesizing several nitrogen-containing molecules used in biological and industrial fields. They have been obtained, as highly regioselective Markovnikov products, by reacting several alkynes with arylamines in the presence of three new N-Heterocyclic carbene gold(I) complexes (3b, 4b, and 6b) together with the known 1-2b and 7b gold complexes as well as silver complexes 1-2a. Gold(I) complexes were investigated by means of NMR, mass spectroscopy, elemental analysis, and X-ray crystallographic studies. Accurate screening of co-catalysts and solvents led to identifying the best reaction conditions and the most active catalyst (2b) in the model hydroamination of phenylacetylene with aniline. Complex 2b was then tested in the hydroamination of alkynes with a wide variety of arylamines yielding a lower percentage of product when arylamines with both electron-withdrawing and electron-donating substituents were involved. Computational studies on the rate-determining step of hydroamination were conducted to shed light on the significantly different yields observed when reacting arylamines with different substituents

Could dietary restrictions affect periodontal disease? A systematic review

ObjectiveThis review aimed at evaluating the possible benefits that caloric restriction (CR) may provide to periodontal disease progression and response to treatment.Material and methodsElectronic search on Medline, Embase and Cochrane, and manual search were performed to identify pre-clinical and on human studies reporting the consequences of CR on clinical and inflammatory parameters related to periodontitis. Newcastle Ottawa System and SYRCLE scale were used to assess the risk of bias.ResultsFour thousand nine hundred eighty articles were initially screened, and a total of 6 articles were finally included, consisting of 4 animal studies and 2 studies in humans. Due to the limited number of studies and heterogeneity of the data, results were presented in descriptive analyses. All studies showed that, compared to the normal (ad libitum) diet, CR might have the potential to reduce the local and systemic hyper-inflammatory state as well as disease progression in periodontal patients.ConclusionsWithin the existing limitations, this review highlights that CR showed some improvements in the periodontal condition by reducing the local and systemic inflammation related to the periodontitis and by improving clinical parameters. However, the results should be interpreted with caution since robust research such as randomized clinical trials is still missing.Clinical relevanceThis review shows that some dietary/caloric restrictions approaches may have the potential to improve periodontal conditions and, in addition, highlights a need for human studies with a robust methodology in order to draw stronger evidence-based conclusions

Synthesis of sericin-based conjugates by click chemistry: enhancement of sunitinib bioavailability and cell membrane permeation

Sericin is a natural protein that has been used in biomedical and pharmaceutical fields as raw material for polypeptide-based drug delivery systems (DDSs). In this paper, it has been employed as pharmaceutical biopolymer for the production of sunitinib–polypeptide conjugate. The synthesis has been carried out by simple click reaction in water, using the redox couple l-ascorbic acid/hydrogen peroxide as a free radical grafting initiator. The bioconjugate molecular weight (50 kDa < Mw < 75 kDa) was obtained by SDS-PAGE, while the spectroscopic characteristics have been studied in order to reveal the presence of grafted sunitinib. In both FT-IR and UV/Vis spectra, signals corresponding to sunitinib functional groups have been identified. Since sunitinib is an anticancer drug characterized by low bioavailability and low permeability, the bioconjugation aimed at their enhancement. In vitro studies demonstrated that bioavailability has been increased to almost 74%, compared with commercial formulation. Also cell membrane permeability has been augmented in in vitro tests, in which membrane models have been used to determine the lipid membrane/physiological fluid partition coefficient (Kp). The log(Kp) value of the bioconjugate was increased to over 4. This effect resulted in a three-fold decrease of IC50 value against MCF-7 cells