Total Molecular Weight Research Articles

Relationship between Segregation Strength and Permeability of Ethanol/Water Mixtures through Block Copolymer Membranes

A series of poly(styrene-b-dimethylsiloxane-b-styrene) (SDS) triblock copolymers with molecular weights ranging from 55 to 150 kg/mol and polydimethylsiloxane (PDMS) volume fractions ranging from 0.59 to 0.83 were used to fabricate membranes for ethanol/water separation by pervaporation. The rigid polystyrene (PS) microphase provides the membrane with structural integrity, while the rubbery PDMS microphase provides nanoscale channels for ethanol transport. We use a simple model to study the effect of morphology and PDMS volume fraction on permeabilitites of ethanol and water through the block copolymer membranes. We defined normalized permeabilities of ethanol and water to account for differences in morphology and PDMS volume fraction. We found that the normalized ethanol permeability in SDS copolymers was independent of the total polymer molecular weight. This is qualitatively different from what was previously reported for poly(styrene-b-butadiene-b-styrene) (SBS) membranes, where the normalized ethanol...

Total and high molecular weight adiponectin and ethnic-specific differences in adiposity and insulin resistance: a cross-sectional study

BackgroundEthnic-specific differences in insulin resistance (IR) are well described but the underlying mechanisms are unknown. Adiponectin is an insulin sensitizing adipocytokine that circulates as multiple isoforms, with high molecular weight (HMW) adiponectin associated with greatest insulin sensitivity. The objective of this study is to determine if plasma total and HMW adiponectin concentrations underlie ethnic-specific differences in IR.MethodsHealthy Canadian Aboriginal, Chinese, European, and South Asian adults (N = 634) were assessed for sociodemographics; lifestyle; fasting plasma insulin, glucose, and total and HMW adiponectin; and adiposity measures [BMI, waist circumference, waist-to-hip ratio, percent body fat, and subcutaneous and visceral adipose tissue (quantified by computed tomography)]. The homeostasis model assessment-insulin resistance (HOMA-IR) assessed IR.ResultsSouth Asians had the greatest HOMA-IR, followed by Aboriginals, Chinese, and Europeans (P < 0.001). Plasma total and HMW adiponectin concentrations were lower in Chinese and South Asians than Aboriginal and Europeans (P < 0.05). Total and HMW adiponectin were inversely associated with HOMA-IR (P < 0.001). Ethnicity modified the relationship between HMW adiponectin and HOMA-IR with stronger effects observed in Aboriginals (P = 0.001), Chinese (P = 0.002), and South Asians (P = 0.040) compared to Europeans. This was not observed for total adiponectin (P = 0.431). At mean total adiponectin concentrations South Asians had higher HOMA-IR than Europeans (P < 0.001).ConclusionsFor each given decrease in HMW adiponectin concentrations a greater increase in HOMA-IR is observed in Aboriginals, Chinese, and South Asians than Europeans. Ethnic-specific differences in HMW adiponectin may account for differences in IR.

Investigating the causal effect of vitamin D on serum adiponectin using a mendelian randomization approach

The aim was to examine the causal effect of vitamin D on serum adiponectin using a multiple instrument Mendelian randomization approach. Serum 25-hydroxy vitamin D (25(OH)D) and serum total or high molecular weight (HMW) adiponectin were measured in two Danish population-based studies: the Inter99 study (6405 adults, 30-60 years) conducted in 1999-2001, and the MONICA10 study (2656 adults, 41-71 years) conducted in 1993-1994. In the Inter99 study, serum 25(OH)D was positively associated with total adiponectin (the effect estimate in % per doubling of 25(OH)D was 4.78, 95% CI: 1.96, 7.68, P<0.001). Using variations in the vitamin D-binding protein gene and the filaggrin gene as instrumental variables, the causal effect in % was estimated to 61.46, 95% CI: 17.51, 120.28, P=0.003 higher adiponectin per doubling of 25(OH)D. In the MONICA10 cohort, no significant association was observed between the serum concentrations of 25(OH)D and HMW adiponectin (the effect estimate in % per doubling of 25(OH)D was -1.51, 95% CI: -5.80, 2.98, P=0.50), although the instrumental variables analysis to some extent supported a positive causal association (the effect estimate in % per doubling of 25(OH)D was 37.13, 95% CI: -3.67, 95.20, P=0.080). The results indicate a possible causal association between serum 25(OH)D and total adiponectin. However, the association was not replicated for HMW adiponectin. Thus, further studies are needed to confirm a causal relationship.

Polymer Molecular Architecture As a Tool for Controlling the Rheological Properties of Aqueous Polyacrylamide Solutions for Enhanced Oil Recovery

The controlled synthesis of high molecular weight branched polyacrylamide (PAM) has been accomplished by using atomic transfer radical polymerization (ATRP) of acrylamide (AM) in water at room temperature. Halogen-functionalized aliphatic polyketones acted as macroinitiators in the polymerization. The obtained branched polymers were used in water solutions to study the effect of the molecular architecture on the rheological properties. For comparison purposes, linear PAM was synthesized by using the same procedure. The intrinsic viscosities and light scattering data suggest that the 13- and 17-arm PAMs are more extended in solution compared to the linear, 4-arm, and 8-arm analogues, at equal total molecular weight. The comparison of linear and 4-, 8-, 12-, 13-, and 17-arm PAM in semidilute solutions demonstrated that the 13- and 17-arm PAM have the highest solution viscosity at equal molecular weight. Depending on the PAM molecular weight and concentration, a significant (as much as 5-fold) increase in so...

HPLC Characterization of Hydrogenous Polystyrene-block-deuterated polystyrene Utilizing the Isotope Effect

HPLC elution behavior of isotopically different block copolymers was investigated. A series of three diblock copolymers of hydrogenous polystyrene and deuterated polystyrene (hPS-b-dPS), in which the length of hPS-block is fixed at 18 kg/mol and the length of dPS-block is varied from 17 kg/mol to 80 kg/mol, was synthesized and their retention behavior in liquid chromatography at critical condition (LCCC) was investigated using a C18 coated silica stationary phase and a mixed solvent of CH2Cl2 and CH3CN. At this LC separation condition, hPS is retained slightly longer than dPS. The LCCC separations were performed at both LCCC conditions of dPS and hPS established with the same stationary and mobile phases, but at different column temperatures. Since the chromatographic retention difference between dPS and hPS is very small, it was possible to elute the block copolymers at both exclusion and interaction modes at the critical condition of each individual block. We found that the block at its critical condition is not fully invisible in both cases. In the LCCC separation at the critical condition of dPS, hPS-b-dPS elutes after the injection solvent peak (interaction mode) due to the stronger interaction of the hPS block. Although they have the same hPS block, they do not coelute but elute in the order of decreasing total molecular weight like an elution in exclusion mode. It clearly demonstrates that the dPS block is not invisible at the critical condition but influences the retention of the block copolymers. Monte Carlo simulations of the partition coefficient of A-b-B into a slit pore were performed to give insight on the elution behavior of A-b-B at the critical condition of the B block. The simulation shows that a block under the critical condition influences the retention of the other visible block whether the visible block is eluted in exclusion or interaction mode. When A is eluted in the interaction mode and B is at its critical condition, the partition coefficient is found to decrease with the increase of the invisible B block length, conforming to the observed elution behavior in experiments.

TNFα blockade for inflammatory rheumatic diseases is associated with a significant gain in android fat mass and has varying effects on adipokines: a 2-year prospective study

To evaluate the long-term consequences of TNFα inhibitors on body composition and fat distribution, as well as changes in serum adipokines in patients with rheumatoid arthritis (RA) or ankylosing spondylitis (AS). Eight patients with RA and twelve with AS requiring a TNFα inhibitor were prospectively followed for 2 years. Body composition was evaluated by dual X-ray absorptiometry and included measurements of total fat mass, lean mass, fat in the gynoid and android regions, and visceral fat. Serum leptin, total and high molecular weight (HMW) adiponectin, resistin, and ghrelin were also assessed. There was a significant gain in body mass index (p = 0.05) and a tendency for weight (p = 0.07), android fat (p = 0.07), and visceral fat (p = 0.059) increase in patients with RA, while in AS, total fat mass significantly increased (p = 0.02) with a parallel weight gain (p = 0.07). When examining the whole population of patients, we observed after 2 years a significant increase in body weight (+1.9%; p = 0.003), body mass index (+2.5%; p = 0.004), total fat mass (+11.1%; p = 0.007), and fat in the android region (+18.3%; p = 0.02). There was a substantial, albeit nonsignificant gain in visceral fat (+24.3%; p = 0.088). Lean mass and gynoid fat were not modified. No major changes were observed for serum leptin, total adiponectin, and ghrelin, while HMW adiponectin and the HMW/total adiponectin ratio tended to decrease (-15.2%, p = 0.057 and -9.3%, p = 0.067, respectively). Resistin decreased significantly (-22.4%, p = 0.01). Long-term TNFα inhibition in RA and AS is associated with a significant gain in fat mass, with a shift to the android (visceral) region. This fat redistribution raises questions about its influence on the cardiovascular profile of patients receiving these treatments.

Infection duration and inflammatory imbalance are associated with atherosclerotic risk in HIV-infected never-smokers independent of antiretroviral therapy

To determine whether the reported increased atherosclerotic risk among HIV-infected individuals is related to antiretroviral therapy (ART) or HIV infection, whether this risk persists in never-smokers, and whether inflammatory profiles are associated with higher risk. Matched cross-sectional study. A total of 100 HIV-infected patients (50 ART-treated >4 years, 50 ART-naive but HIV-infected >2 years) and 50 HIV-negative controls were recruited in age-matched never-smoking male triads (mean age 40.2 years). Carotid intima-media maximal thickness (c-IMT) was measured across 12 sites. Pro-inflammatory [highly sensitive C-reactive protein (hs-CRP), resistin, interleukin-6, interleukin-18, insulin, serum amyloid A, D-dimer) and anti-inflammatory (total and high molecular weight adiponectin, interleukin-27, interleukin-10) markers were dichotomized into high/low scores (based on median values). c-IMT was compared across HIV/treatment groups or inflammatory profiles using linear regression models adjusted for age, diabetes, hypertension, and, for HIV-infected patients, nadir CD4 cell counts. Although adjusted c-IMT initially tended to be thicker in ART-exposed patients (P=0.2), in post-hoc analyses stratifying by median HIV duration we observed significantly higher adjusted c-IMT in patients with longer (>7.9 years: 0.760±0.008 mm) versus shorter prevalent duration of known HIV infection (<7.9 years: 0.731±0.008 mm, P=0.02), which remained significant after additionally adjusting for ART (P=0.04). Individuals with low anti-inflammatory profile (<median versus >median score) had thicker c-IMT (0.754±0.006mm versus 0.722±0.006 mm, P<0.001), with anti-inflammatory markers declining as prevalent duration of HIV infection increased (P for linear trend <0.001). Known HIV duration is related to thicker c-IMT, irrespective of ART, in these carefully selected age-matched never-smoking HIV-treated and ART-naive male individuals. Higher levels of anti-inflammatory markers appeared protective for atherosclerosis.

Adipose tissue depot and cell size dependency of adiponectin synthesis and secretion in human obesity

Adiponectin is an insulin sensitizing fat cell (FC) hormone whose levels are related to adipose tissue (AT) mass and depot distribution. We hypothesized that the nature of AT expansion (hypertrophy vs. hyperplasia) contributes to obesity-related reductions in serum adiponectin and that this effect is influenced by the regional distribution of AT to subcutaneous (S) and visceral (V) depots. Thirteen obese subjects provided paired AT biopsies. Serum total and high molecular weight (HMW) adiponectin levels were determined by ELISA. Secretion was quantified following 24-h explant culture. FC size, number, % large, and % small FC were determined by microscopic analysis. Secretion of total adiponectin was highest by SAT (P = 0.008) and correlated more strongly with serum adiponectin (total: P = 0.015, r = 0.77; HMW: P = 0.005, r = 0.83) than did secretion by VAT (P = 0.05, r = 0.66 for both). FC size was greatest in SAT and correlated negatively with both serum (total: P = 0.01, r = −0.74; HMW: P = 0.03, r = −0.69) and secreted (total: P = 0.05, r = −0.72; HMW: P = 0.02, r = −0.87) adiponectin. The % small FC in SAT correlated positively with both serum (total: P = 0.006, r = 0.87; HMW: P = 0.009, r = 0.79) and secreted (total: P = 0.03, r = 0.75; HMW: P = 0.01, r = 0.92) adiponectin. VAT FC size correlated negatively with serum HMW adiponectin (P = 0.01, r = −0.76) but not with any measure of secretion. VAT had the greatest % small FC, which related positively to serum HMW (P = 0.004, r = 0.81) and to secreted total adiponectin (P = 0.02, r = 0.78). These studies indicate that differences in fat cell size and depot distribution of AT expansion are important influences on adiponectin in obesity.

Ovarian HMW adiponectin is associated with folliculogenesis in women with polycystic ovary syndrome

BackgroundAdiponectin may regulate ovarian steroidogenesis, folliculogenesis and ovulation. The alterations in the distribution of adiponectin multimers in follicular fluid (FF) and the relationship between adiponectin multimers and folliculogenesis in women with polycystic ovary syndrome (PCOS) remain unclear. In this study, we aimed to investigate the association between the levels of total and high molecular weight (HMW) adiponectin in serum and FF and folliculogenesis in women undergoing in vitro fertilisation (IVF).MethodsThis prospective study included ten Chinese women with PCOS and ten controls undergoing IVF. The levels of the total and HMW adiponectin in serum and FF were determined by ELISA. Insulin resistance (IR) was estimated using the homeostasis model assessment insulin resistance index (HOMA-IR).ResultsAfter controlling for the body mass index (BMI), the levels of the total, and the HMW adiponectin in the serum and FF were significantly lower in the women with PCOS compared with the normovulatory women undergoing IVF (P < 0.05). The levels of the HMW adiponectin were significantly lower in the FF than in the serum (P < 0.01). No significant differences were found in the total adiponectin levels in the serum and in the FF (P > 0.05). Decreased HMW adiponectin in the FF was associated with an increased number of follicles and decreased follicular diameters in the normovulatory and PCOS women, and this association was independent of the overall adiposity. A strong positive linear correlation was observed between the number of the follicles and the IR estimated by HOMA-IR (r = 0.784, P < 0.0001). We found that the larger follicular diameters had a negative relationship with the IR estimated by HOMA-IR (r = −0.445, P < 0.05). A strong negative linear correlation was observed between HOMA-IR and the HMW adiponectin levels (r = −0.726, P < 0.001) and the total adiponectin levels (r = −0.759, P < 0.001) in the FF.ConclusionsThe levels of the total adiponectin and the HMW adiponectin in the FF and serum were decreased in the Chinese women with PCOS compared with the normovulatory women undergoing IVF, and the differences persisted after controlling for the BMI. Ovarian HMW adiponectin is negatively correlated to folliculogenesis.

Long-chain branched polymers to prolong homogeneous stretching and to resist melt breakup

We explored a new synthetic strategy for ultra-high molecular weight long-chain branched (LCB) polymers with equal spacing between adjacent branch points. This method can synthesize LCB polystyrene (LCB-PS) with total molecular weight of 4.9 million g/mole, 16 branches of 140 kg/mole and polydispersity index of 1.5. The introduction of multiple branch points with long side chains allows the LCB-PS to resist the elastic-driven decohesion. Even after a large step extension of stretching ratio λ = 7.4, the specimen would not undergo elastic breakup that occurs in linear PS even at λ = 2.7. These LCB-PSs are also extraordinarily more stretchable during startup uniaxial extension, with the maximum engineering stress emerging at stretching ratio λmax≈4Mbb/Me, where Mbb is the molecular weight of backbone and Me is the molecular weight between entanglements.

Total and high-molecular-weight adiponectin levels in relation to insulin resistance among overweight/obese adults.

ObjectiveTo determine whether baseline levels or intervention-associated changes in total and high molecular weight (HMW) adiponectin levels were associated with insulin resistance after six months of behavioral treatment for weight loss.DesignAn ancillary study to a behavioral weight loss trial; the intervention was delivered in group sessions.MethodsParticipants included 143 overweight/obese adults with a mean BMI of 33.7 kg/m2. The sample was 88% female, 67% white, and 44.2 ± 8.5 years old. Circulating adiponectin levels (total and HMW) and the homeostasis model assessment (HOMA) of insulin resistance were measured and evaluated.ResultsAt baseline, there was significant inverse associations between total adiponectin and HOMA (p < 0.001) and between HMW adiponectin and HOMA (p < 0.001) independent of weight. At 6-mo, there was a 17% improvement in HOMA, 8% increase in total adiponectin, 17% increase in HMW adiponectin levels, and 8.72% weight loss (p’s for all< 0.001). There was also a significant inverse association between changes in total adiponectin and HOMA (p = 0.04) that was independent of baseline weight and weight loss. In contrast, the association between changes in HMW adiponectin and HOMA was attenuated after adjustment for weight loss.ConclusionsAn increased level of total adiponectin was associated with improved insulin sensitivity, regardless of baseline weight and weight loss. However, baseline total and HMW adiponectin levels were more strongly associated with HOMA than changes in these measures at six months. HMW adiponectin level was not related more closely to insulin resistance than total adiponectin level.

Online monitoring of reaction temperature during cationic ring opening polymerization of epichlorohydrin in presence of BF3 and 1,4‐butanediol

ABSTRACTThis work introduces cationic ring opening polymerization of polyepichlorohydrin (PECH) produced under various reaction conditions (set temperature: −10 to 40°C, [C]/[I] ratio: 0.1–1, monomer feed rate: 1–4 mL/min). In addition, a correlation between the exothermic reaction temperature and the performance of the PECH was obtained by utilizing a reaction temperature monitoring system, GPC, 1H‐NMR, and FTIR. During the polymerization, an induction period which affects the polydispersity was observed below 10°C. At lower temperatures and lower [C]/[I] ratios, a higher induction period was observed. The monomer feed rate did not affect the induction period but it highly affected the polydispersity when the induction period occurred. The total molecular weight of PECH increased with decreasing set temperature even though the amount of low molecular weight cyclic oligomer increased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39912.

Adiponectin gene variants, adiponectin isoforms and cardiometabolic risk in type 2 diabetic patients.

The aim of the present study was to examine the associations of rs2241766 (+45T>G), rs1501299 (+276G>T), rs17300539 (-11391G>A) and rs182052 (-10069G>A) in the adiponectin (Ad) gene with adiponectin concentrations, and concomitantly the association of these variants with cardiometabolic risk in type 2 diabetic patients of African ancestry. A cross-sectional study of 200 patients was carried out. Concentrations of total, high (HMW), middle (MMW) and low (LMW) molecular weight adiponectin isoforms were measured. The four polymorphisms were genotyped. Decreased values were noted for total Ad in overweight, dyslipidemia and coronary artery disease (CAD), for HMW in overweight and dyslipidemia, for MMW in CAD, for LMW in dyslipidemia and CAD, for the percentage HMW/total in overweight, and for MMW:HMW ratio in patients without hypertriglyceridemic waist (HTGW). Significant associations were noted between total Ad, HMW, and HMW/total Ad and rs182052 under a dominant model (P=0.04, P=0.03 and P=0.04, respectively), and between MMW and rs17300539 (P=0.006). No significant difference in adiponectin concentrations was noted according to rs2241766 and rs1501299 genotypes. Patients carrying the rs2241766 G allele (TG+GG) had an increased risk of HTGW (odds ratio [OR] 3.1; P=0.04) and of CAD (OR 3.3; P=0.01). The odds of having low total adiponectin concentrations (<25th percentile: 3.49ng/mL) for carrying the rs182052A allele (AA+GA) was: OR 0.40; P=0.009. The single-nucleotide polymorphism associated with adiponectin levels was not concomitantly associated with cardiometabolic risk factors. Adiponectin concentrations and ADIPOQ variants are implicated in the pathophysiological process leading to cardiovascular diseases, but the genetic effects seem to be independent of adiponectin concentrations in our Afro-Caribbean diabetic patients.

Adipocytokines and cytokeratin-18 in patients with nonalcoholic fatty liver disease: Introduction of CHA index

Background and rationale. Insulin resistance (IR), adipocytokines, oxidative stress and hepatic apoptosis play a pathogenetic role in nonalcoholic fatty liver disease (NAFLD).Aims. The evaluation of specific adipocytokines and markers of IR, oxidative stress and apoptosis in NAFLD patients; the introduction of a combined non-invasive index for nonalcoholic steatohepatitis (NASH).Material and methods. Thirty patients with biopsy-proven NAFLD (15 with simple nonalcoholic fatty liver [NAFL], 15 with NASH) and 24 controls were recruited. Blood samples for total and high molecular weight (HMW) adiponectin, visfatin and tumor necrosis factor (TNF)-α, the apoptotic by-product cytokeratin (CK)–18, the reactive oxygen metabolites (ROMs) and standard biochemical tests were measured. Homeostatic model of assessment - insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were calculated. Main results: Total and HMW adiponectin were significantly lower and TNF-a higher in either NAFL or NASH group compared to control group; CK–18 was significantly higher in NASH compared to either NAFL or control group. CHAI (an acronym of CK–18, HOMA-IR, AST Index) was calculated as the product of parameters being significantly different between NAFL and NASH groups. CHAI was significantly higher in NASH (24.2 [15.1–214.0]) compared to either NAFL (15.7 [6.8–22.7]) or control (5.1 [2.4–7.6]) group (p < 0.001) and significantly higher as the severity of steatosis, fibrosis, ballooning, lobular and portal inflammation advanced.Conclusion. CHAI was escalating from controls to NAFL and NASH and was higher by increasing the severity of all the main histo-logical lesions. However, a validation study is needed before introducing CHAI in clinical practice.

A3-3: Pre-Pregnancy Adiponectin Levels and Subsequent Risk of Gestational Diabetes Mellitus (GDM)

Background/Aims Adiponectin is an adipocyte-derived polypeptide with insulin-sensitizing properties that has been prospectively linked to the development of type 2 diabetes. Adiponectin levels decrease during the course of normal pregnancy. It is unknown whether pre-pregnancy adiponectin levels are related to risk of gestational diabetes mellitus (GDM), a common pregnancy complication and strong predictor of type 2 diabetes. Our study assessed prospectively whether serum total and high molecular weight (HMW) adiponectin concentrations measured before pregnancy are associated with subsequent risk of GDM.

Adipocytokine levels in women with anorexia nervosa. Relationship with weight restoration and disease duration

Starvation-induced depletion of fat stores in anorexia nervosa (AN) is known to be accompanied by alterations in some circulating adipocytokines. We analyzed a panel of circulating adipocytokines in women with AN compared with normal-weight controls and their relation with the disease duration and weight restoration. We analyzed circulating adipocytokine levels in 28 patients with AN and in 33 normal-weight controls who were eating healthily. We determined by enzyme-linked immunosorbent assay the circulating levels of total and high molecular weight (HMW) adiponectin, lipocalin-2 (LCN2), leptin, tumor necrosis factor receptor-II (TNFRII), interleukin-6 (IL6), adipocyte fatty acid binding protein-4 (FABP4), ghrelin, and resistin. The two circulating forms of adiponectin are higher in AN women compared with controls. Both total and HMW adiponectin related negatively to the duration of the disease (r = -0.372, p = 0.033; r = -0.450, p = 0.038, respectively). Furthermore, the lipid binding-proteins LCN2 and FABP4 are lower in AN compared to the control group. Finally, leptin levels are lower in AN against controls and correlated positively with disease duration (r = 0.537, p = 0.007). Resistin, ghrelin, TNFRII, and IL6 have similar values in both groups, although TNFRII and ghrelin related negatively to body mass index variation at the end of treatment (r = -0.456, p = 0.039; r = -0.536, p = 0.015, respectively). These results suggest there is a need to investigate if changes in adipocytokine levels could serve as weight restoration biomarkers. Further studies are warranted to elucidate the specific role of these molecules in the timing of weight restoration.

Branched polyacrylamides: Synthesis and effect of molecular architecture on solution rheology

Linear, star and comb-like polyacrylamides (PAM) have been prepared by atomic transfer radical polymerization (ATRP) in aqueous media at room temperature. The influence of the molecular architecture of PAM on the rheological properties in aqueous solution has been investigated. The well-known theory of increased entanglement density by branching for polymers in the melt can also be applied to polymers in the semi-dilute water solutions. We have demonstrated this by investigating the rheological properties of PAM of similar molecular weights with different molecular architectures. Interestingly, the solution viscosity of a comb PAM is higher compared to its linear and star analogues (both at equal span molecular weight, Mn,SPAN, and total molecular weight, Mn,tot). In addition to the pure viscosity, we also demonstrate that the visco-elastic properties of the polymeric solutions depend significantly on the molecular architecture of the employed PAM. The elastic response of water solutions containing comb PAM is more pronounced than for solutions containing either linear or star PAM at similar Mn,SPAN and Mn,tot. The obtained results pave the way for application of these polymeric materials in Enhanced Oil Recovery (EOR).

Characterization of a large glycoprotein proteoglycan by size-exclusion chromatography combined with light and X-ray scattering methods

The molecular weight and chain conformation of a proteoglycan derived from shark cartilage in solution were characterized by size-exclusion chromatography combined with low-angle laser light scattering and small-angle X-ray scattering methods. The total molecular weight of the proteoglycan was 3.9±0.2 million and the molecular weight of the main component was about 2.0±0.2 million. The X-ray scattering data revealed that the main components of the proteoglycan are nearly equal to a chain with excluded volume and their persistence lengths range from 13.5 to 16.4nm. These results show that size-exclusion chromatography combined with low-angle laser light scattering and small-angle X-ray scattering measurements are complementarily useful for characterization of large biopolymers in solution.

Random measurements of adiponectin and IL‐6 may not be indicative of the 24‐h profile in critically ill patients

The anti-inflammatory role of adiponectin has prompted interest in a potential role in acute inflammatory conditions associated with critical illness. It is unclear whether a random adiponectin measurement adequately reflects the 24-h profile in critically ill patients. To assess the temporal profile of total and high molecular weight (HMW) adiponectin and interleukin-6 (IL-6) in 15 critically ill patients. A prospective, observational study. Level II intensive care unit in a metropolitan hospital. Fifteen critically ill patients expected to stay in the ICU for longer than 48 h were eligible for enrolment. None. Serial, hourly measurements of total and HMW adiponectin and IL-6. Over a 24-h period, total and HMW adiponectin display considerable within-patient variability (coefficient of variation 34% and 87% respectively) and show no trend over time. Averaging 2 or 3 continuous measures reduced within-patient variability of both total and HMW adiponectin by up to 50% compared to one measure. There was a negative correlation between serum glucose and adiponectin (total P = 0·016, HMW P = 0·039). No relationship existed between adiponectin and IL-6 (total P = 0·62, HMW P = 0·35). Marked within-patient, hourly variability in total and HMW adiponectin is evident in critically ill patients. A random measurement may not be reflective of the 24-h profile in these patients. A negative correlation exists between adiponectin and blood glucose levels and a positive correlation between adiponectin and oxygen saturation. No clear relationship exists between adiponectin and IL-6.

Poly(lactic acid) polymer stars built from early generation dendritic polyols

A family of polymer stars has been prepared from early generation dendritic cores with four, six, and eight arms. Four dendritic cores were prepared from the sequential reaction of a multifunctional alcohol with a protected anhydride, followed by deprotection to afford two or three new alcohol functionalities per reactive site. These cores were used as initiators for the tin-catalyzed ring-opening polymerization of l-lactide and rac-lactide to afford isotactic and atactic degradable stars, respectively. Two series of stars were prepared for each monomer, either maintaining total molecular weight or number of monomer units per arm. The polymers were characterized by NMR spectroscopy, light-scattering gel-permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Our results support previous work that suggests that the length of the arms dictates thermal properties rather than the total molecular weight of the star. Little effect was noted between aromatic and aliphatic cores, presumably due to the flexibility of the rest of the core molecule. We have shown that early generation dendrimers can serve as excellent core structures for building core-first polymer stars via the ring-opening of cyclic esters.