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1
Lange, K., C. Dominik e A. G. G. M. Tielens. "Stability of polycyclic aromatic hydrocarbon clusters in protoplanetary discs". Astronomy & Astrophysics 653 (settembre 2021): A21. http://dx.doi.org/10.1051/0004-6361/202140590.
Abstract (sommario):
Context. The infrared signature of polycyclic aromatic hydrocarbons (PAHs) is present in many protostellar discs, and these species are thought to play an important role in the heating of the gas in the photosphere. Aims. We consider PAH cluster formation as one possible cause for non-detections of PAH features in protoplanetary discs. We test the necessary conditions for cluster formation and cluster dissociation by stellar optical and far-UV photons in protoplanetary discs using a Herbig Ae/Be and a T Tauri star disc model. Methods. We perform Monte Carlo and statistical calculations to determine dissociation rates for coronene, circumcoronene, and circumcoronene clusters with sizes of between 2 and 200 cluster members. By applying general disc models to our Herbig Ae/Be and T Tauri star model, we estimate the formation rate of PAH dimers and compare these with the dissociation rates. Results. We show that the formation of PAH dimers can take place in the inner 100 AU of protoplanetary discs in sub-photospheric layers. Dimer formation takes seconds to years, allowing them to grow beyond dimer size in a short time. We further demonstrate that PAH clusters increase their stability while they grow when they are located beyond a critical distance that depends on stellar properties and PAH species. The comparison with the local vertical mixing timescale allows a determination of the minimum cluster size necessary for the survival of PAH clusters. Conclusions. Considering the PAH cluster formation sites, cluster survival in the photosphere of the inner disc of Herbig stars is unlikely because of the high UV radiation. For the T Tauri stars, survival of coronene, circumcoronene, and circumcircumcoronene clusters is possible, and cluster formation should be considered as one possible explanation for low PAH detection rates in T Tauri star discs.
2
Adamson, Brian A., Scott A. Skeen, Musahid Ahmed e Nils Hansen. "Nucleation of soot: experimental assessment of the role of polycyclic aromatic hydrocarbon (PAH) dimers". Zeitschrift für Physikalische Chemie 234, n. 7-9 (27 agosto 2020): 1295–310. http://dx.doi.org/10.1515/zpch-2020-1638.
Abstract (sommario):
AbstractThe irreversible dimerization of polycyclic aromatic hydrocarbons (PAHs) – typically pyrene (C16H10) dimerization – is widely used in combustion chemistry models to describe the soot particle inception step. This paper concerns itself with the detection and identification of dimers of flame-synthesized PAH radicals and closed-shell molecules and an experimental assessment of the role of these PAH dimers for the nucleation of soot. To this end, flame-generated species were extracted from an inverse co-flow flame of ethylene at atmospheric pressure and immediately diluted with excess nitrogen before the mixture was analyzed using flame-sampling tandem mass spectrometry with collision-induced fragmentation. Signal at m/z = 404.157 (C32H20) and m/z = 452.157 (C36H20) were detected and identified as dimers of closed-shell C16H10 and C18H10 monomers, respectively. A complex between a C13H9 radical and a C24H12 closed-shell PAH was observed at m/z = 465.164 (C37H21). However, a rigorous analysis of the flame-sampled mass spectra as a function of the dilution ratio, defined as the ratio of the flow rates of the diluent nitrogen to the sampled gases, indicates that the observed dimers are not flame-born, but are produced in the sampling line. In agreement with theoretical considerations, this paper provides experimental evidence that pyrene dimers cannot be a key intermediate in particle inception at elevated flame temperatures.
3
Webster, Ian J., Jacob L. Beckham, Natalie D. Johnson e Michael A. Duncan. "Photochemical Synthesis and Spectroscopy of Covalent PAH Dimers". Journal of Physical Chemistry A 126, n. 7 (12 febbraio 2022): 1144–57. http://dx.doi.org/10.1021/acs.jpca.1c10606.
4
Mao, Qian, Juan Zhou, Kai H. Luo e Adri C. T. van Duin. "Atomistic insights into the dynamics of binary collisions between gaseous molecules and polycyclic aromatic hydrocarbon dimers". Physical Chemistry Chemical Physics 21, n. 7 (2019): 3849–56. http://dx.doi.org/10.1039/c8cp07060a.
5
Mercier, X., O. Carrivain, C. Irimiea, A. Faccinetto e E. Therssen. "Dimers of polycyclic aromatic hydrocarbons: the missing pieces in the soot formation process". Physical Chemistry Chemical Physics 21, n. 16 (2019): 8282–94. http://dx.doi.org/10.1039/c9cp00394k.
6
Zemskova, Marina, Nolan McClain, Maki Niihori, Mathews V. Varghese, Joel James, Ruslan Rafikov e Olga Rafikova. "Necrosis-Released HMGB1 (High Mobility Group Box 1) in the Progressive Pulmonary Arterial Hypertension Associated With Male Sex". Hypertension 76, n. 6 (dicembre 2020): 1787–99. http://dx.doi.org/10.1161/hypertensionaha.120.16118.
Abstract (sommario):
Damage-associated molecular patterns, such as HMGB1 (high mobility group box 1), play a well-recognized role in the development of pulmonary arterial hypertension (PAH), a progressive fatal disease of the pulmonary vasculature. However, the contribution of the particular type of vascular cells, type of cell death, or the form of released HMGB1 in PAH remains unclear. Moreover, although male patients with PAH show a higher level of circulating HMGB1, its involvement in the severe PAH phenotype reported in males is unknown. In this study, we aimed to investigate the sources and active forms of HMGB1 released from damaged vascular cells and their contribution to the progressive type of PAH in males. Our results showed that HMGB1 is released by either pulmonary artery human endothelial cells or human pulmonary artery smooth muscle cells that underwent necrotic cell death, although only human pulmonary artery smooth muscle cells produce HMGB1 during apoptosis. Moreover, only human pulmonary artery smooth muscle cell death induced a release of dimeric HMGB1, found to be mitochondrial reactive oxygen species dependent, and TLR4 (toll-like receptor 4) activation. The modified Sugen/Hypoxia rat model replicates the human sexual dimorphism in PAH severity (right ventricle systolic pressure in males versus females 54.7±2.3 versus 44.6±2 mm Hg). By using this model, we confirmed that necroptosis and necrosis are the primary sources of circulating HMGB1 in the male rats, although only necrosis increased circulation of HMGB1 dimers. Attenuation of necrosis but not apoptosis or necroptosis prevented TLR4 activation in males and blunted the sex differences in PAH severity. We conclude that necrosis, through the release of HMGB1 dimers, predisposes males to a progressive form of PAH.
7
Kholghy, M. R., G. A. Kelesidis e S. E. Pratsinis. "Reactive polycyclic aromatic hydrocarbon dimerization drives soot nucleation". Physical Chemistry Chemical Physics 20, n. 16 (2018): 10926–38. http://dx.doi.org/10.1039/c7cp07803j.
Abstract (sommario):
Nucleation is an important yet poorly understood step in soot formation. Strong chemical bonds between PAH monomers are required as physical dimerization cannot explain soot formation at high temperatures. Dimers can be considered as soot nuclei as larger oligomers have negligible contribution.
8
Calvo, F., E. Yurtsever e Ö. Birer. "Possible Formation of Metastable PAH Dimers upon Pickup by Helium Droplets". Journal of Physical Chemistry A 120, n. 10 (4 marzo 2016): 1727–36. http://dx.doi.org/10.1021/acs.jpca.5b12394.
9
Yuditskaya, Susan, Ashaunta Tumblin, Gerard T. Hoehn, Guanghui Wang, Steven K. Drake, Xiuli Xu, Saixia Ying et al. "Proteomic identification of altered apolipoprotein patterns in pulmonary hypertension and vasculopathy of sickle cell disease". Blood 113, n. 5 (29 gennaio 2009): 1122–28. http://dx.doi.org/10.1182/blood-2008-03-142604.
Abstract (sommario):
Abstract Pulmonary arterial hypertension (PAH) is emerging as a major complication and independent risk factor for death among adults with sickle cell disease (SCD). Using surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF MS), we searched for biomarkers of PAH in plasma specimens from 27 homozygous sickle cell anemia (HbSS) patients with PAH and 28 without PAH. In PAH patients, analysis consistently showed lower abundance of a 28.1-kDa peak (P < .001), identified by high-resolution mass spectrometry as the oxidant-scavenging protein apolipoprotein A-I (apoA-I), which correlated with clinical assays of apoA-I (r = .58, P < .001) and high-density lipoprotein (HDL) levels (r = .50, P = .001). Consistent with endothelial dysfunction that may mediate this effect in PAH, HbSS patients with lower apoA-I levels also displayed impaired vasodilatory responses to acetylcholine (mean ± SEM, 189% ± 34% [n = 13] vs 339% ± 51% [n = 13], P < .001). As a group, patients with SCD demonstrated significantly lower apoA-I levels than African-American control subjects. The PAH cohort was further characterized by high levels of apolipoproteins A-II and B and serum amyloid A, and low levels of haptoglobin dimers and plasminogen. These results imply a relationship of apolipoproteins to the development of PAH vasculopathy in SCD, potentially involving an unexpected mechanistic parallel to atherosclerosis, another proliferative vasculopathy.
10
Giaccai, Jennifer A., e J. Houston Miller. "Examination of the electronic structure of oxygen-containing PAH dimers and trimers". Proceedings of the Combustion Institute 37, n. 1 (2019): 903–10. http://dx.doi.org/10.1016/j.proci.2018.05.057.
11
Cherchneff, I. "Nucleating Dust in Carbon-Rich AGB Stars". Symposium - International Astronomical Union 177 (2000): 331–36. http://dx.doi.org/10.1017/s0074180900002576.
Abstract (sommario):
Chemical models of the inner circumstellar envelope of a typical carbon-rich AGB star are presented. The effect of pulsation-driven shocks on the gas close to the stellar photosphere is considered. The chemistry of dust condensation nuclei formation is described and applied to the gas layers close to the star. We derive formation yields for polycyclic aromatic hydrocarbon (PAH) species and their dimers and discuss their role in the condensation of dust.
12
Cherchneff, I. "Chemical models of AGB winds". Symposium - International Astronomical Union 178 (1997): 469–76. http://dx.doi.org/10.1017/s0074180900009621.
Abstract (sommario):
We present chemical models of the inner circumstellar envelope of a typical carbon-rich AGB star. The effect of pulsation-driven shocks on the gas close to the stellar photosphere is considered. The chemistry of dust condensation nuclei formation is described and applied to the gas layers close to the star. We derive formation yields for polycyclic aromatic hydrocarbon (PAH) species and their dimers and discuss their role in the condensation of dust. Models of the chemistry of silicon- and sulfur-bearing molecules in the inner envelope are also presented.
13
Brulé, Cédric, Fatima Sultana, Sandro Hollenstein, Takao Okazaki e Kenneth K. Laali. "Superacid-Catalyzed Dimerization/Cyclization of Isopropenyl-PAHs - Novel Pathways to PAH Dimers, Phenalenes and Their Stable Carbocations". European Journal of Organic Chemistry 2008, n. 21 (11 giugno 2008): 3700–3708. http://dx.doi.org/10.1002/ejoc.200800252.
14
Cate, Hugo, Arina ten Cate-Hoek e Marie-Claire Kleinegris. "D-dimer as a marker for cardiovascular and arterial thrombotic events in patients with peripheral arterial disease". Thrombosis and Haemostasis 110, n. 08 (2013): 233–43. http://dx.doi.org/10.1160/th13-01-0032.
Abstract (sommario):
SummaryPeripheral artery disease (PAD) is associated with an increased risk for cardiovascular events. D-dimers are a marker for hypercoagulability and are linked with thrombotic events in patients with venous as well as arterial thrombosis. The predictive value of plasma D-dimer levels in relation to cardiovascular events in patients with PAD is not unambiguously established. It was our objective to gather evidence evaluating the value of D-dimer as a predictor of arterial thrombotic events patients with PAD. The Pubmed, Embase, and Cochrane databases were searched (January 1980-November 2012), and 65 abstracts were found. The strategy was supplemented with manual review of reference lists. Case-control, cohort or prospective cohort studies that measured fibrin D-dimer in patients with PAD, were included. Studies were excluded if there was no follow-up for arterial thrombotic events or when no specific information on D-dimer was available. The search yielded 10 studies for our analysis, comprising 2,420 patients with PAD, with a total of 1,036 cardiovascular events in 10,599 patient-years. Two studies with a follow-up of one year showed that fibrin D-dimer predicts both deterioration of PAD and subsequent thrombotic events. Five out of six studies with a median follow-up of 2–4 years revealed that an increased D-dimer is predictive of various arterial thrombotic events including mortality. Two studies with a longer follow-up (over 6 years) did not show an independent association between increased D-dimer levels, arterial thrombotic events and CVD mortality. In conclusion, an increased D-dimer appeared to be independently associated with a two times increased risk of near-term cardiovascular events (relative risk 2.30, 95% confidence interval 1.43–3.68). However formal meta-analysis was only feasible for four out of 10 included studies. Due to the extended heterogeneity of the included studies cautious interpretation of these data is warranted.
15
Mutoh, Katsuya, Hiroki Arai, Yoichi Kobayashi e Jiro Abe. "Photo-control of the thermal radical recombination reaction: photochromism of an azobenzene-bridged imidazole dimer". Pure and Applied Chemistry 87, n. 6 (1 giugno 2015): 511–23. http://dx.doi.org/10.1515/pac-2014-0910.
Abstract (sommario):
AbstractAmong various kinds of photochromic compounds, bridged imidazole dimers have been known as fast photo-switch molecules. Bridged imidazole dimers have opened up various potential applications to photochromic lenses and real-time holographic displays. The optical properties of bridged imidazole dimers strongly depend on the bridging moiety to tether two imidazole rings. Therefore, the control of the bridging structure by introducing another photochromic moiety would increase the versatility of bridged imidazole dimers. In this study, we designed and synthesized a new type of the bridged imidazole dimer 1 which has the azobenzene moiety as the photo-responsive linker. The cis–trans isomerization of the azobenzene moiety enables to change the distance between the photogenerated radical pairs. The two structural isomers, cis–1 and trans–1, are observed and both compounds undergo the photochromism to produce the imidazolyl radicals. We found that the two imidazolyl radicals generated from cis–1 are close enough to form the intramolecular C–N bond, whereas the imidazolyl radicals of trans–1 undergo the intermolecular recombination reaction due to the long distance between the radicals. Our results demonstrate the control of intra-/intermolecular radical recombination reactions by the combination of the two photochromic compounds.
16
Bleeker, Wim K., Jessica L. Teeling, Arthur J. Verhoeven, Gemma M. M. Rigter, Jacques Agterberg, Anton T. J. Tool, Anky H. L. Koenderman, Taco W. Kuijpers e C. Erik Hack. "Vasoactive side effects of intravenous immunoglobulin preparations in a rat model and their treatment with recombinant platelet-activating factor acetylhydrolase". Blood 95, n. 5 (1 marzo 2000): 1856–61. http://dx.doi.org/10.1182/blood.v95.5.1856.005k03_1856_1861.
Abstract (sommario):
Previously, we observed in a rat model that intravenous administration of intramuscular immunoglobulin preparations induced a long-lasting hypotension, which appeared to be associated with the presence of IgG polymers and dimers in the preparations, but unrelated to complement activation. We found evidence that this hypotensive response is mediated by platelet-activating factor (PAF) produced by macrophages. In this study, we compared the vasoactive effects of 16 intravenous immunoglobulin (IVIG) products from 10 different manufacturers, in anesthetized rats. Eight of the IVIG preparations showed no hypotensive effects (less than 15% decrease), whereas the other 8 had relatively strong effects (15%-50% decrease). The hypotensive effects correlated with the IgG dimer content of the preparations. Pretreatment of the rats with recombinant PAF acetylhydrolase completely prevented the hypotensive reaction on IVIG infusion, and administration after the onset of hypotension resulted in normalization of the blood pressure. We also observed PAF production on in vitro incubation of human neutrophils with IVIG, which could be blocked by anti-Fcγ receptor antibodies. This indicates that induction of PAF generation may also occur in a human system. Our findings support the hypothesis that the clinical side effects of IVIG in patients may be caused by macrophage and neutrophil activation through interaction of IgG dimers with Fcγ receptors. Because phagocyte activation may also lead to the release of other inflammatory mediators, recombinant PAF acetylhydrolase (rPAF-AH) provides a useful tool to determine whether PAF plays a role in the clinical side effects of IVIG. If so, rPAF-AH can be used for the treatment of those adverse reactions.
17
Rosenthal, Esther C. E. "From vanadium(V) to vanadium(IV) - and backwards". Pure and Applied Chemistry 81, n. 7 (30 giugno 2009): 1197–204. http://dx.doi.org/10.1351/pac-con-08-08-32.
Abstract (sommario):
With bidentate alkoxy alkoxide and alkoxy alcohol ligands, respectively, a series of oxovanadium complexes in the oxidation state +4 is synthesized starting from oxovanadium(V) compounds. The reaction of two or more equivalents of 2-methoxyethanol with VOCl3 in n-hexane yields a mixture of the monomeric oxovanadium(IV) complex cis-[VOCl2(HOCH2CH2OMe-κ2O)(HOCH2CH2OMe-κO1)] and the alkoxide-bridged oxovanadium(IV) dimer syn-[VOCl(µ-OCH2CH2OMe-κ2O)]2, which are separated by fractionated crystallization. The same reaction with 2-ethoxy- and 2-iso-propoxyethanol gives only the alkoxide-bridged oxovanadium(IV) dimers anti-[VOCl(µ-OCH2CH2OR-κ2O)]2 (R = Et, iPr). All alkoxide bridged oxovanadium(IV) dimers are furthermore obtained as decomposition products of the chloride-bridged oxovanadium(V) complexes [VO(µ-Cl)Cl(OCH2CH2OR-κ2O)]2 (R = Me, Et, iPr) by Cl2 elimination and react inversely with Cl2 to the vanadium(V) compounds.
18
Leme-Kraus, A. A., R. S. Phansalkar, M. C. dos Reis, B. Aydin, A. B. S. Sousa, Y. Alania, J. McAlpine, S. N. Chen, G. F. Pauli e A. K. Bedran-Russo. "Dimeric Proanthocyanidins on the Stability of Dentin and Adhesive Biointerfaces". Journal of Dental Research 99, n. 2 (11 dicembre 2019): 175–81. http://dx.doi.org/10.1177/0022034519892959.
Abstract (sommario):
A dentin biomodification strategy with selective proanthocyanidin (PAC)–enriched extracts reinforces dentin and dentin-resin interfaces. Enrichment of the extracts according to the degree of polymerization allows exploration of bioactive principles of PACs and structure-activity relationships. This study investigated the sustained dentin matrix biomodification and dentin-resin bioadhesion of 2 fractions consisting exclusively of B-type PAC dimers with or without a single galloyl motif (specifically, DIMERG and DIMERNG) and their precursor material, enriched grape seed extract (e-GSE; Vitis vinifera). The biomodification potential was determined by long-term evaluation of the apparent modulus of elasticity and collagen solubility (hydroxyproline release). Chemical characterization of the dentin matrix was performed by attenuated total reflectance–Fourier-transform infrared spectroscopy. The bioadhesive properties were assessed by a microtensile bond strength test at different time points, and macro-hybrid layers were produced to verify the degree of conversion of the adhesive resin. Fractions consisting of DIMERG, DIMERNG, and their precursor, e-GSE, increased the modulus of elasticity at all time points and reduced collagen degradation. Specimens treated with DIMERNG remained stable throughout 12 mo of storage, whereas a significant drop in the modulus of elasticity was observed for the DIMERG and e-GSE groups at 6 mo. The fractions and precursor did not affect the degree of resin conversion at the hybrid layer. Changes in infrared resonances corresponding to collagen cross-links in the dentin matrix occurred for all treatments. Higher bond strength was observed for dentin treated with e-GSE as compared with DIMERG and DIMERNG; all biointerfaces remained stable after 12 mo. Nongalloylated PACs mediate stable dentin biomodification, which includes protective activity against collagen degradation and reinforcement of the anchoring dentin matrix. Collectively, PACs with a higher degree of oligomerization offer a robust bioadhesion between the hydrophilic dentin matrix and the hydrophobic adhesive.
19
Suk, Jae-min, Min Kyung Chae e Kyu-Sung Jeong. "Indolocarbazole-based anion receptors and molecular switches". Pure and Applied Chemistry 84, n. 4 (14 febbraio 2012): 953–64. http://dx.doi.org/10.1351/pac-con-11-10-02.
Abstract (sommario):
A number of indolocarbazole-based anion receptors were prepared and their anion-binding behaviors were characterized in solution and in the solid state. First, chain-length-dependent binding affinities of chloride ion were revealed using a series of indolocarbazoles that consisted of one to four indolocarbazole units. The binding affinities were steadily enhanced from monomer to dimer, then to trimer by Gibb’s free energy (–∆∆G) = 2.4 ± 0.1 kcal/mol, and then nearly saturated. Second, a water-soluble trimer folded to generate an internal helical cavity with six convergent NHs, wherein small halides bound in water in the order of Cl– (65 M–1) > F– (46 M–1), and Br– (19 M–1). Third, X-ray crystal structures clearly proved helical folding of a trimer in the presence of sulfate ion, in which left- and right-handed helices stacked alternatively. It was also shown that the selectivity of anion binding could be varied by the modification of the spacer groups connecting indolocarbazole units. Finally, we prepared chiral indolocabazole dimers that adopted helical structures by intramolecular hydrogen bonds and displayed complete inversion of the helical sense upon anion binding. The dimers gave characteristic optical readouts in a reversible manner according to chemical stimuli, thus functioning as chirooptical molecular switches.
20
Zagrapan, Branislav, Johannes Klopf, Nihan Dide Celem, Annika Brandau, Patrick Rossi, Yulia Gordeeva, Alexandra Regina Szewczyk et al. "Diagnostic Utility of a Combined MPO/D-Dimer Score to Distinguish Abdominal Aortic Aneurysm from Peripheral Artery Disease". Journal of Clinical Medicine 12, n. 24 (7 dicembre 2023): 7558. http://dx.doi.org/10.3390/jcm12247558.
Abstract (sommario):
Abdominal aortic aneurysm (AAA) and peripheral artery disease (PAD) share pathophysiological mechanisms including the activation of the fibrinolytic and innate immune system, which explains the analysis of D-dimer and myeloperoxidase (MPO) in both conditions. This study evaluates the diagnostic marker potential of both variables separately and as a combined MPO/D-dimer score for identifying patients with AAA versus healthy individuals or patients with PAD. Plasma levels of MPO and D-dimer were increased in PAD and AAA compared to healthy controls (median for MPO: 13.63 ng/mL [AAA] vs. 11.74 ng/mL [PAD] vs. 9.16 ng/mL [healthy], D-dimer: 1.27 μg/mL [AAA] vs. 0.58 μg/mL [PAD] vs. 0.38 μg/mL [healthy]). The combined MPO/D-dimer score (median 1.26 [AAA] vs. −0.19 [PAD] vs. −0.93 [healthy]) showed an improved performance in distinguishing AAA from PAD when analysed using the receiver operating characteristic curve (area under the curve) for AAA against the pooled data of healthy controls + PAD: 0.728 [MPO], 0.749 [D-dimer], 0.801 [score]. Diagnostic sensitivity and specificity ranged at 82.9% and 70.2% (for score cut-off = 0). These findings were confirmed for a separate collective of AAA patients with 35% simultaneous PAD. Thus, evaluating MPO together with D-dimer in a simple score may be useful for diagnostic detection and the distinction of AAA from athero-occlusive diseases like PAD.
21
Et.al, Tamilarasi C. "Degree based and neighbourhood degree-sum based topological indices of PAH(Dimer 1) in graphene context". Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, n. 3 (10 aprile 2021): 3642–49. http://dx.doi.org/10.17762/turcomat.v12i3.1645.
Abstract (sommario):
In this paper, twenty degree-based topological indices and seven neighbourhood degree-sum-based topological indices of Dimer 1 (two units of chrysene) [4] 0D & 1D in the graphene context are enumerated. The Oligomer Approach[3] is practiced here to explore the interconnection between PAH ( cove type periphery based on 11, 11’-dibromo-5,5’-bis chrysene as a key monomer-Dimer 1) and graphene numerically through the indices.
22
Arfan, Sara, Abdelrahman Zamzam, Muzammil H. Syed, Shubha Jain, Niousha Jahanpour, Rawand Abdin e Mohammad Qadura. "The Clinical Utility of D-Dimer and Prothrombin Fragment (F1+2) for Peripheral Artery Disease: A Prospective Study". Biomedicines 10, n. 4 (11 aprile 2022): 878. http://dx.doi.org/10.3390/biomedicines10040878.
Abstract (sommario):
D-dimer and prothrombin fragment (F1+2) levels are elevated in patients with peripheral artery disease (PAD). We examined their prognostic potential in predicting decreasing ABI and major adverse limb events (MALE). A total of 206 patients were recruited from St. Michael’s Hospital and followed for two years. Baseline plasma concentrations of D-dimer and F1+2 were recorded. Pearson’s correlation was used to assess the correlation between the biomarkers and ABI at year 2. During follow-up, multivariable Cox proportional hazard analysis was performed to investigate their role in predicting decreasing ABI (defined as change in ABI > −0.15) and MALE (defined as the need for arterial intervention or major limb amputation). Cumulative survival was assessed using Kaplan–Meier analysis. Baseline D-dimer and F1+2 levels were elevated in PAD patients (median (IQR) 1.34 (0.80–2.20) for D-dimer and 3.60 (2.30–4.74) for F1+2; p = 0.001) compared to non-PAD controls (median (IQR) 0.69 (0.29–1.20) for D-dimer and 1.84 (1.17–3.09) for F1+2; p = 0.001). Both markers were negatively correlated with ABI at year 2 (r = −0.231 for D-dimer, r = −0.49 for F1+2; p = 0.001). Cox analysis demonstrated F1+2 and D-dimer to be independent predictors of PAD status (HR = 1.27, 95% CI = 1.15–1.54; p = 0.013 for D-dimer and HR = 1.28, 95% CI = 1.14–1.58; p = 0.019 for F1+2). Elevated baseline concentrations of D-dimer and F1+2 were associated with high incidence of decreasing ABI and 1- and 2-year event-free survival (62% and 86%, respectively). Combined analysis of D-dimer and F1+2 provides important prognostic information that facilitates risk stratification for future disease progression and MALE outcomes in patients with PAD.
23
Gardana, Claudio, e Paolo Simonetti. "Evaluation of the Degree of Polymerization of the Proanthocyanidins in Cranberry by Molecular Sieving and Characterization of the Low Molecular Weight Fractions by UHPLC-Orbitrap Mass Spectrometry". Molecules 24, n. 8 (17 aprile 2019): 1504. http://dx.doi.org/10.3390/molecules24081504.
Abstract (sommario):
4-dimethylammino-cinnamaldehyde (DMAC) assays quantify total proanthocyanidins (PACs) but do not provide qualitative PAC molecular weight distribution information and cannot discriminate between A- and B-type PACs. We developed an efficient method for assessing PAC molecular weight distributions. The PACs from three commercial cranberry extracts (A1–A3) were fractionated by molecular sieves with cut-offs of 3, 10, 30, 50, and 100 kDa, and each fraction was analyzed by DMAC assays. A1, A2, and A3 contained 27%, 33%, and 15% PACs, respectively. Approximately 28 PACs, 20 flavonols, and 15 phenolic acids were identified by UHPLC-DAD-Orbitrap MS in A1 and A3, while A2 contained only flavan-3-ols. Epicatechin was the main monomer in A1 and A3, and catechin was the main in A2. Procyanidin A2 was the main dimer in A1 and A3, representing more than 85% of the total dimers, while it constituted approximately only 24% of A2. A1 and A3 contained quercetin, isorhamnetin, myricetin, and their glycosides, which were totally absent in A2. In A1 and A3 the PACs were mainly distributed in the fractions 30–3 and <3 kDa, while in A2 more than 70% were present in the fraction less than 3 kDa. Overall, obtained data strongly suggests that A2 is not cranberry-derived, or is adulterated with another source of PACs.
24
Nifant’ev, Ilya, Pavel Ivchenko, Alexander Tavtorkin, Alexey Vinogradov e Alexander Vinogradov. "Non-traditional Ziegler-Natta catalysis in α-olefin transformations: reaction mechanisms and product design". Pure and Applied Chemistry 89, n. 8 (26 luglio 2017): 1017–32. http://dx.doi.org/10.1515/pac-2016-1131.
Abstract (sommario):
AbstractThis paper describes our recent results in the field of zirconocene-catalyzed α-oltfin transformations, and focuses on questions regarding the reaction mechanism, rational design of zirconocene pre-catalysts, as well as prospective uses of α-olefin products. It has been determined that a wide range of α-olefin-based products, namely vinylidene dimers, oligomers and polymers, can be prepared via catalysis by zirconocene dichlorides, activated by a minimal (10–20 eq.) amount of MAO. We assumed that in the presence of minimal quantities of MAO, various types of zirconocene catalysts form different types of catalytic particles. In the case of bis-cyclopentadienyl complexes, the reactive center is formed under the influence of R2AlCl, which makes the chain termination via β-hydride elimination significantly easier, with α-olefin dimers being formed as the primary product. Bis-indenyl complexes and their heteroanalogues, form stable cationic catalytic particles and effectively catalyze the polymerization. Mono-indenyl and mono-substituted bis-cyclopentadienyl-ansa complexes catalyze α-olefin oligomerization. Effective catalysts of dimerization, oligomerization and polymerization of α-olefins in the presence of minimal MAO quantities are proposed. Prospects of using α-olefin dimers, oligomers and polymers in the synthesis of branched hydrocarbon functional derivatives (dimers), high quality, low viscosity motor oils (oligomers), and thickeners and absorbents (polymers) are examined.
25
Iwasaki, Yosuke, e Tomoyasu Aihara. "3217 Molecular dynamics study of behavior of PAH dimer in exhaust gas". Proceedings of the JSME annual meeting 2005.3 (2005): 115–16. http://dx.doi.org/10.1299/jsmemecjo.2005.3.0_115.
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Mahmoodinia, Mehdi, Mahsa Ebadi, Per-Olof Åstrand, De Chen, Hong-Ye Cheng e Yi-An Zhu. "Structural and electronic properties of the Ptn–PAH complex (n = 1, 2) from density functional calculations". Phys. Chem. Chem. Phys. 16, n. 34 (2014): 18586–95. http://dx.doi.org/10.1039/c4cp02488e.
Abstract (sommario):
The catalytic activity of the Pt atom and dimer can be changed by modifying its chemical surroundings and single layers of Pt atoms have a different catalytic activity as compared to Pt clusters on a carbon surface.
27
Goldstein, Jake, Robert S. Dieter, Vinod Bansal, Keaton Wieschhaus, Robert S. Dieter, Emily Bontekoe, Debra Hoppensteadt e Jawed Fareed. "Arterial-renal Syndrome in Patients with ESRD, a New Disease Paradigm". Clinical and Applied Thrombosis/Hemostasis 28 (gennaio 2022): 107602962110728. http://dx.doi.org/10.1177/10760296211072820.
Abstract (sommario):
Background Patients with end-stage renal disease (ESRD) often present with an increased risk of cardiovascular disease. Conditions of compromised cardiovascular health such as atrial fibrillation (AFIB) and peripheral arterial disease (PAD) may alter biomarker levels in a way that reflects worsening ESRD. This study profiled biomarkers and laboratory parameters of endothelium dysfunction in patients with ESRD, categorized by additional AFIB and PAD conditions. Methods Citrated blood samples were collected from 95 patients with ESRD. Biomarker levels were measured from plasma samples using sandwich ELISAs, including tissue plasminogen activator (tPA), D-dimer, and nitrotyrosine. Lab parameters, including BUN, calcium, creatinine, parathyroid hormone, phosphate, alkaline phosphatase, ferritin, transferrin, and total iron capacity, and patient comorbidities were obtained from patient medical records. The comorbidities were determined through provider notes, and evidence of applicable testing. Results 14.89% of patients were found to have atrial fibrillation (n = 14), 30.85% of patients were found to have peripheral arterial disease (n = 29), and 6.38% of patients were found to have both peripheral arterial disease and atrial fibrillation (n = 6). When compared to patients with only ESRD, patients with ESRD and PAD showed elevated levels of D-Dimer (p = .0314) and nitrotyrosine (p = .0330). When compared to patients with only ESRD, patients with atrial fibrillation showed elevated levels of D-Dimer (p = .0372), nitrotyrosine (p = .0322), and tPA (p = .0198). Conclusion When compared to patients with just ESRD, patients with concomitant PAD had elevated levels of Nitrotyrosine and D-dimer; while patients with concomitant Afib had elevated levels of nitrotyrosine, D-dimer, as well as tPA.
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Lázár, Károly. "Redistribution of iron ions in porous ferrisilicates during redox treatments". Pure and Applied Chemistry 89, n. 4 (1 aprile 2017): 471–79. http://dx.doi.org/10.1515/pac-2016-1026.
Abstract (sommario):
Abstract Relocation of iron ions in microporous Fe-FER, (Al+Fe)-FER, Fe-MFI (FER: ferrierite, MFI: silicalite) and in mesoporous Fe-MCM-41 ferrisilicate (MCM: Mobile Crystalline Material) samples was followed during redox treatments primarily by tool of the in situ Mössbauer spectroscopy. Coexistence of various Fe3+ and Fe2+ species is demonstrated. In microporous Fe-FER and Fe-MFI existence of combined μ-oxo iron dimers, Fe3+FW-O-Fe2+EFW can be proposed. The presence of these dimers can easily be correlated with catalytic effect shown in certain oxidation processes. Structural rearrangement can also be revealed in mesoporous Fe-MCM-41 which result in improvement of catalytic performance in CO oxidation.
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Kroese, Andries, Einar Stranden, Britt Morken, Gunnar Sandbæk, Anne Lindahl, Harald Arnesen, Ingebjørg Seljeflot e Marthe Nylænde. "Prothrombotic activity is associated with the anatomical as well as the functional severity of peripheral arterial occlusive disease". Thrombosis and Haemostasis 95, n. 04 (2006): 702–7. http://dx.doi.org/10.1160/th06-01-0007.
Abstract (sommario):
SummaryThe importance of prothrombotic activity in cardiovascular disease has been well established. However, limited data exist on the relationship between prothrombotic activity and the severity of peripheral arterial occlusive disease (PAD).The objective of the present study was to investigate the relationship between markers of haemostasis and the diagnostic measures of PAD: ankle-brachial-index (ABI), maximum treadmill walking distance and angiographic score. In a cross-sectional study of 127 patients (mean age 66 years; 64% males) with angiographically verified PAD, fasting blood samples were drawn, and citrated plasma was obtained for determination of selected haemostatic variables: von Willebrand factor (vWF), thrombomodulin (sTM), thrombin-antithrombin complex (TAT), soluble tissue factor (sTF), tPA antigen (tPAag) and D-dimer were all significantly correlated with the angiographic score (p<0.05 for all). D-dimer, tPAag and fibrinogen were inversely correlated with the maximum treadmill walking distance, (p<0.0001, p<0.04 and p<0.05, respectively), whereas fibrinogen was the only variable correlating to ABI (r = –0.223, p<0.05). After adjustment for relevant covariates, D-dimer and TAT remained statistically significantly associated with the angiographic score (p<0.001), and fibrinogen was, independent of other risk factors, inversely related with both the maximum treadmill walking distance and the ABI (p<0.01 for both).This rather large study in patients with PAD showed that plasma levels of D-dimer, TAT and fibrinogen significantly predicted the extent of atherosclerosis, evaluated by angiographic score, maximum treadmill walking distance and ABI, respectively. These findings demonstrate a prothrombotic state in PAD patients, which might be of importance in future diagnosis and treatment of the disease.
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Templeton, Douglas M., e Kerstin Moehle. "Structural aspects of molecular recognition in the immune system. Part I: Acquired immunity (IUPAC Technical Report)". Pure and Applied Chemistry 86, n. 10 (21 ottobre 2014): 1435–81. http://dx.doi.org/10.1515/pac-2013-1020.
Abstract (sommario):
Abstract Humoral immunity allows the body to mount a defense against pathogens and foreign substances, and to respond with memory to subsequent exposures. The molecular participants may also recognize self-structures, leading to attack on the body and autoimmune disease. The main players in humoral immunity are antibody-producing B lymphocytes, and several classes of T lymphocytes. This review deals with the molecular details of recognition of antigens by soluble antibodies, and of substances presented to receptors on the surfaces of T cells (TCRs). The prototype antibody consists of a dimer of dimers, two heavy (H) chains and two light (L) chains, with antigen recognition capacity lying in variable “head” regions of an H-L pair. Most crystallographic studies are done with this substructure, called a Fab fragment, bound in a soluble antigen complex. Homologous to this arrangement, the prototype TCR consists of two chains (α and β) that complex not soluble antigen, but usually a short peptide or other small molecule presented by proteins of the major histocompatibility complex. In each case a general background on the historical development of understanding the molecular recognition interface is given, followed by a number of examples of crystal structures from the recent literature that have allowed us to refine our understanding of the complex recognition process. Variations on the prototypical structures are also considered. The spectrum of recognition strategies involves interplay of lock-and-key with flexibility, varying degrees of entropic and enthalpic contributions, surface shaping by entrapped water molecules, and combinations of stabilizing hydrogen bonding, electrostatic interactions, salt bridging, and van der Waals forces. Preeminent in the recent literature are details of antibody binding to influenza A and human immunodeficiency viral antigens. Both viral antigens and attempts to understand autoimmunity are prominent in the recent TCR literature.
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Fang, Run, Xian-Su Cheng e Wu-Shi Lin. "Preparation and application of dimer acid/lignin graft copolymer". BioResources 6, n. 3 (15 giugno 2011): 2874–84. http://dx.doi.org/10.15376/biores.6.3.2874-2884.
Abstract (sommario):
Dimer acid (DA) was grafted onto lignin (EHL) to form a graft copolymer DA-g-EHL. The selection of the reaction type and the optimization of the reaction conditions for the grafting reaction were conducted through orthogonal and single factor experiments. FT-IR and thermal analysis were used to characterize the graft product. It was found that, compared with free radical grafting, DA can be grafted onto EHL more effectively by ester condensation with strongly acidic cation exchange resin as a catalyst. Under optimum reaction conditions, the increase of acid value and the yield of graft copolymer can reach about 9.3% and 83%, respectively. The application of DA-g-EHL in preparing modified phenolic aldehyde amine curing agent (PAA) was studied. Results showed that the flexibility of the epoxy resin cured by DA-g-EHL modified PAA is significant higher than that of the resin cured by EHL modified PAA. The graft of DA onto EHL may reduce the rigidity of EHL and the chain stiffness of the PAA modified by EHL.
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Heinrich, Jürgen, Helmut Schulte, Rainer Schönfeld, Ekkehart Köhler e Gerd Assmann. "Association of Variables of Coagulation, Fibrinolysis and Acute-phase with Atherosclerosis in Coronary and Peripheral Arteries and those Arteries Supplying the Brain". Thrombosis and Haemostasis 73, n. 03 (1995): 374–79. http://dx.doi.org/10.1055/s-0038-1653783.
Abstract (sommario):
SummaryWe investigated the vessel status of coronary and peripheral arteries and those arteries supplying the brain in 929 consecutive male patients admitted to a coronary rehabilitation unit. The severity of coronary atherosclerosis was scored using coronary angiography. Changes in extracranial brain vessels and manifest cerebrovascular disease (CVD) were determined by B-mode ultrasound and Doppler examination. Peripheral arterial disease (PAD) was diagnosed using base-line and stress oscillography. We assessed variables of coagulation, fibrinolysis, and the acute phase response.There was a significant increase in plasma fibrinogen, plasminogen, d-dimer and C-reactive protein (CRP) with increasing severity of coronary heart disease. Compared to men with unaffected arteries, men with 3 diseased coronary arteries had 58% greater d-dimer concentrations. Patients with CVD and PAD, respectively, also had significantly higher fibrinogen, d-dimer and CRP concentrations. We did not find an association between plasminogen activator inhibitor activity and the severity of coronary atherosclerosis.In conclusion, plasma fibrinogen, d-dimer and CRP concentrations were significantly related to atherosclerosis in the coronary, peripheral and extracranial brain arteries.
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Spruell, Jason M. "Molecular recognition and switching via radical dimerization". Pure and Applied Chemistry 82, n. 12 (30 settembre 2010): 2281–94. http://dx.doi.org/10.1351/pac-con-10-08-03.
Abstract (sommario):
This article highlights the emerging use of the interactions of radical π-dimers to drive both molecular recognition and switching processes within supramolecular systems and mechanically interlocked molecular architectures. The enhanced stability experienced by dimers of radical cation species when encapsulated, as compared to when they are free in solution, is driving their useful incorporation into functional systems. The redox stimulation used in the production of radical cation species provides the ideal trigger for molecular switching events. Moreover, the nature and strength of the radical dimerization events introduces a completely novel recognition motif within supramolecular and mechanically interlocked molecular systems, complementing well-established techniques and enabling new research opportunities to blossom.
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Ikramuddin, Farha, Tanya Melnik, Nicholas E. Ingraham, Nguyen Nguyen, Lianne Siegel, Michael G. Usher, Christopher J. Tignanelli e Leslie Morse. "Predictors of discharge disposition and mortality following hospitalization with SARS-CoV-2 infection". PLOS ONE 18, n. 4 (13 aprile 2023): e0283326. http://dx.doi.org/10.1371/journal.pone.0283326.
Abstract (sommario):
Importance The SARS-CoV-2 pandemic has overwhelmed hospital capacity, prioritizing the need to understand factors associated with type of discharge disposition. Objective Characterization of disposition associated factors following SARS-CoV-2. Design Retrospective study of SARS-CoV-2 positive patients from March 7th, 2020, to May 4th, 2022, requiring hospitalization. Setting Midwest academic health-system. Participants Patients above the age 18 years admitted with PCR + SARS-CoV-2. Intervention None. Main outcomes Discharge to home versus PAC (inpatient rehabilitation facility (IRF), skilled-nursing facility (SNF), long-term acute care (LTACH)), or died/hospice while hospitalized (DH). Results We identified 62,279 SARS-CoV-2 PCR+ patients; 6,248 required hospitalizations, of whom 4611(73.8%) were discharged home, 985 (15.8%) to PAC and 652 (10.4%) died in hospital (DH). Patients discharged to PAC had a higher median age (75.7 years, IQR: 65.6–85.1) compared to those discharged home (57.0 years, IQR: 38.2–69.9), and had longer mean length of stay (LOS) 14.7 days, SD: 14.0) compared to discharge home (5.8 days, SD: 5.9). Older age (RRR:1.04, 95% CI:1.041–1.055), and higher Elixhauser comorbidity index [EI] (RRR:1.19, 95% CI:1.168–1.218) were associated with higher rate of discharge to PAC versus home. Older age (RRR:1.069, 95% CI:1.060–1.077) and higher EI (RRR:1.09, 95% CI:1.071–1.126) were associated with more frequent DH versus home. Blacks, Asians, and Hispanics were less likely to be discharged to PAC (RRR, 0.64 CI 0.47–0.88), (RRR 0.48 CI 0.34–0.67) and (RRR 0.586 CI 0.352–0.975). Having alpha variant was associated with less frequent PAC discharge versus home (RRR 0.589 CI 0.444–780). The relative risks for DH were lower with a higher platelet count 0.998 (CI 0.99–0.99) and albumin levels 0.342 (CI 0.26–0.45), and higher with increased CRP (RRR 1.006 CI 1.004–1.007) and D-Dimer (RRR 1.070 CI 1.039–1.101). Increased albumin had lower risk to PAC discharge (RRR 0.630 CI 0.497–0.798. An increase in D-Dimer (RRR1.033 CI 1.002–1.064) and CRP (RRR1.002 CI1.001–1.004) was associated with higher risk of PAC discharge. A breakthrough (BT) infection was associated with lower likelihood of DH and PAC. Conclusion Older age, higher EI, CRP and D-Dimer are associated with PAC and DH discharges following hospitalization with COVID-19 infection. BT infection reduces the likelihood of being discharged to PAC and DH.
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Iannuzzo, Fortuna, Vincenzo Piccolo, Ettore Novellino, Elisabetta Schiano, Emanuela Salviati, Vincenzo Summa, Pietro Campiglia, Gian Carlo Tenore e Maria Maisto. "A Food-Grade Method for Enhancing the Levels of Low Molecular Weight Proanthocyanidins with Potentially High Intestinal Bioavailability". International Journal of Molecular Sciences 23, n. 21 (4 novembre 2022): 13557. http://dx.doi.org/10.3390/ijms232113557.
Abstract (sommario):
Proanthocyanidins (PACs) are a group of bioactive molecules found in a variety of plants and foods. Their bioavailability depends on their molecular size, with monomers and dimers being more bioavailable than those that have a higher polymerization degree. This study aimed to develop a method to convert high-molecular-weight PACs to low-molecular-weight ones in a grape seed extract (GSE) from Vitis vinifera L. Therefore, GSE was subjected to alkaline treatment (ATGSE), and its difference in chemical composition, compared to GSE, was evaluated using a molecular networking (MN) approach based on results obtained from HPLC-ESI HRMS/MS characterization analysis. The network analysis mainly noted the PAC cluster with about 142 PAC compounds identified. In particular, the obtained results showed a higher content of monomeric and dimeric PACs in ATGSE compared to GSE, with 58% and 49% monomers and 31% and 24% dimers, respectively. Conversely, trimeric (9%), polymeric (4%), and galloylated PACs (14%) were more abundant in GSE than in ATGSE (6%, 1%, and 4%, respectively). Moreover, in vitro antioxidant and anti-inflammatory activities were investigated, showing the high beneficial potential of both extracts. In conclusion, ATGSE could represent an innovative natural matrix rich in bioavailable and bioaccessible PACs for nutraceutical applications with potential beneficial properties.
36
Tang, Zeyuan, e Bjørk Hammer. "Dimerization of dehydrogenated polycyclic aromatic hydrocarbons on graphene". Journal of Chemical Physics 156, n. 13 (7 aprile 2022): 134703. http://dx.doi.org/10.1063/5.0083253.
Abstract (sommario):
Dimerization of polycyclic aromatic hydrocarbons (PAHs) is an important, yet poorly understood, step in the on-surface synthesis of graphene (nanoribbon), soot formation, and growth of carbonaceous dust grains in the interstellar medium (ISM). The on-surface synthesis of graphene and the growth of carbonaceous dust grains in the ISM require the chemical dimerization in which chemical bonds are formed between PAH monomers. An accurate and cheap method of exploring structure rearrangements is needed to reveal the mechanism of chemical dimerization on surfaces. This work has investigated the chemical dimerization of two dehydrogenated PAHs (coronene and pentacene) on graphene via an evolutionary algorithm augmented by machine learning surrogate potentials and a set of customized structure operators. Different dimer structures on surfaces have been successfully located by our structure search methods. Their binding energies are within the experimental errors of temperature programmed desorption measurements. The mechanism of coronene dimer formation on graphene is further studied and discussed.
37
Kremers, Bram, Lina Wübbeke, Barend Mees, Hugo ten Cate, Henri Spronk e Arina ten Cate-Hoek. "Plasma Biomarkers to Predict Cardiovascular Outcome in Patients With Peripheral Artery Disease". Arteriosclerosis, Thrombosis, and Vascular Biology 40, n. 9 (settembre 2020): 2018–32. http://dx.doi.org/10.1161/atvbaha.120.314774.
Abstract (sommario):
Objective: Patients with lower extremity peripheral artery disease (PAD) are at increased risk of major adverse cardiovascular events. Numerous plasma biomarkers have been investigated in lower extremity PAD, but none are used for clinical risk assessment. We aimed to provide a comprehensive overview of biomarker testing in PAD as a first step to improve risk stratification. Approach and Results: A systematic literature review in MEDLINE/PubMed, Cochrane, and Embase was performed, identifying all studies investigating plasma biomarkers in association with cardiovascular events and mortality in lower extremity PAD. Forty-seven studies comprising 21 473 PAD patients met our criteria and were included. Effect estimates were provided by the studies based on a minimum follow-up of 1 year. Meta-analyses were performed by pooling studies per biomarker for each end point. Patients with increased high-sensitivity CRP (C-reactive protein) levels had a relative risk of 1.86 (1.48–2.33) for major adverse cardiovascular events and a relative risk of 3.49 (2.35–5.19) for mortality. Increased fibrinogen and d -dimer levels were associated with an increased relative risk of mortality of 2.08 (1.46–2.97) and 2.22 (1.24–3.98), respectively. Additionally, patients with increased NT-proBNP (N-terminal pro-B-type natriuretic peptide) and high-sensitivity cTnT (cardiac troponin T) levels were at an even higher risk of mortality with relative risks of 4.50 (2.98–6.81) and 3.33 (2.70–4.10), respectively. Conclusions: This systematic review identifies promising biomarkers representing different pathophysiological processes implicated in lower extremity PAD, including high-sensitivity CRP, neutrophil-lymphocyte ratio, fibrinogen, d -dimer, NT-proBNP, and high-sensitivity cTnT. Clinical implementation should be preceded by a management study to test the utility of a combination of these markers for individual risk stratification. Ultimately, this may contribute to tailored treatment and increased effectiveness of current treatment strategies in PAD.
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Koski, M. Kristian, Jothi Anantharajan, Petri Kursula, Prathusha Dhavala, Abhinandan V. Murthy, Ulrich Bergmann, Johanna Myllyharju e Rik K. Wierenga. "Assembly of the elongated collagen prolyl 4-hydroxylase α2β2 heterotetramer around a central α2 dimer". Biochemical Journal 474, n. 5 (20 febbraio 2017): 751–69. http://dx.doi.org/10.1042/bcj20161000.
Abstract (sommario):
Collagen prolyl 4-hydroxylase (C-P4H), an α2β2 heterotetramer, is a crucial enzyme for collagen synthesis. The α-subunit consists of an N-terminal dimerization domain, a central peptide substrate-binding (PSB) domain, and a C-terminal catalytic (CAT) domain. The β-subunit [also known as protein disulfide isomerase (PDI)] acts as a chaperone, stabilizing the functional conformation of C-P4H. C-P4H has been studied for decades, but its structure has remained elusive. Here, we present a three-dimensional small-angle X-ray scattering model of the entire human C-P4H-I heterotetramer. C-P4H is an elongated, bilobal, symmetric molecule with a length of 290 Å. The dimerization domains from the two α-subunits form a protein–protein dimer interface, assembled around the central antiparallel coiled-coil interface of their N-terminal α-helices. This region forms a thin waist in the bilobal tetramer. The two PSB/CAT units, each complexed with a PDI/β-subunit, form two bulky lobes pointing outward from this waist region, such that the PDI/β-subunits locate at the far ends of the βααβ complex. The PDI/β-subunit interacts extensively with the CAT domain. The asymmetric shape of two truncated C-P4H-I variants, also characterized in the present study, agrees with this assembly. Furthermore, data from these truncated variants show that dimerization between the α-subunits has an important role in achieving the correct PSB–CAT assembly competent for catalytic activity. Kinetic assays with various proline-rich peptide substrates and inhibitors suggest that, in the competent assembly, the PSB domain binds to the procollagen substrate downstream from the CAT domain.
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Fabón, Gabriel, Laura Monforte, Rafael Tomás-Las-Heras, Encarnación Núñez-Olivera e Javier Martínez-Abaigar. "Ultraviolet radiation-induced DNA damage in bryophytes: what is already known and new results on rapid repair in a liverwort in an artificial diel cycle." Boletín de la Sociedad Española de Briología, n. 37(31) (15 novembre 2011): 39–52. http://dx.doi.org/10.58469/bseb.2011.42.14.007.
Abstract (sommario):
We studied, under laboratory conditions, the diel variations of DNA damage in response to changes in ultraviolet (UV) radiation in the liverwort Jungermannia exsertifolia subsp. cordifolia. The samples were exposed to three radiation regimes: P (only photosynthetically active radiation, PAR), PA (PAR + UV-A), and PAB (PAR + UV-A + UV-B). The day was divided in four periods: darkness, a first low-PAR period, a high-PAR plus UV period, and a second low-PAR period. After 15 days of culture, we measured the amount of thymine dimers in the four periods of the day on two consecutive days. DNA damage was significantly stronger in PAB than in P and PA samples, which corroborates the fact that it is a good and considerably specific biomarker of artificially enhanced UV-B. The diel changes in DNA damage consisted of a significant increase in thymine dimers at the end of the period of high-PAR plus UV, followed by a quick and complete repair after UV cessation and the instauration of low-PAR. These diel changes occurred much more clearly in PAB samples than in PA and P samples, and thus the differences in DNA damage were mainly due to UV-B. The low amount of thymine dimers produced and the rapid repair indicated that the UV-B levels applied caused little DNA damage in this liverwort, which is well adapted to those UV-B levels. This is the first time in which diel variations in DNA damage in response to artificial changes in UV-B are detected in a liverwort. Se han estudiado, en condiciones de laboratorio, los daños producidos en el ADN de la hepática Jungermannia exsertifolia subsp. cordifolia por exposición a la radiación ultravioleta (UV) a lo largo de ciclos diarios artificiales de 24 horas. Las muestras se expusieron a tres regímenes de radiación: P (con sólo radiación fotosintéticamente activa, PAR), PA (PAR + UV-A), y PAB (PAR + UV-A + UV-B). El día se dividió en cuatro periodos: oscuridad, un primer periodo de baja PAR, un periodo de alta PAR más radiación UV, y un segundo periodo de baja PAR. Después de 15 días de cultivo, se midió la cantidad de dímeros de timina en los cuatro periodos del día en dos días consecutivos. Los daños en el ADN fueron significativamente mayores en las muestras PAB que en las P y PA, lo que confirma que es un biomarcador bueno y considerablemente específico del aumento artificial de la radiación UV-B. Con respecto a los cambios en el ciclo diario, el número de dímeros de timina aumentó significativamente al final del periodo de alta PAR más radiación UV, y posteriormente se produjo una reparación rápida y completa de los daños tras el apagado de la radiación UV y la instauración del segundo periodo de baja PAR. Estos cambios fueron mucho más claros en las muestras PAB que en las P y PA, por lo que las diferencias en los daños al ADN se debieron principalmente a la radiación UV-B. La baja cantidad de dímeros de timina producidos y la rapidez de la reparación indican que los niveles de radiación UV-B aplicados provocaban pocos daños en el ADN de esta especie, que por lo tanto está bien adaptada a dichos niveles. Ésta es la primera vez que se detectan variaciones en los daños al ADN de una hepática en respuesta a cambios artificiales de UV-B a lo largo del ciclo diario.
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Monteiro, Júlia L., Natália M. Moreira, Deborah A. dos Santos, Márcio W. Paixão e Arlene G. Corrêa. "Step economy strategy for the synthesis of amphoteric aminoaldehydes, key intermediates for reduced hydantoins". Pure and Applied Chemistry 90, n. 1 (26 gennaio 2018): 121–32. http://dx.doi.org/10.1515/pac-2017-0705.
Abstract (sommario):
AbstractDespite of the orthogonal reactivity of the N–H aziridines aldehyde, these compounds exist as an equilibrium of three different forms – whereas the dimeric one is mostly observed in a variety of solvents. In this work, we have developed an alternative protocol for the aminoaldehyde dimers synthesis in two steps starting with an organocatalyzed aziridination between α,β-unsaturated aldehydes and a protected amine to afford known isolable and stable N-protected aziridine aldehydes. After Boc-deprotection, dimeric species were immediately formed from monomeric N–H aziridine aldehydes. From this building-block new reduced hydantoins were prepared via [3+2]-annulation with isocyanates.
41
Vert, Michel, Jiazhong Chen, Karl-Heinz Hellwich, Philip Hodge, Tamaki Nakano, Carmen Scholz, Stanislaw Slomkowski e Jiri Vohlidal. "Nomenclature and terminology for linear lactic acid-based polymers (IUPAC Recommendations 2019)". Pure and Applied Chemistry 92, n. 1 (28 gennaio 2020): 193–211. http://dx.doi.org/10.1515/pac-2017-1007.
Abstract (sommario):
AbstractLactic acid enantiomers and cyclic lactic acid dimers, the latter referred to as lactides, are sources of degradable aliphatic polymers that are composed of chiral constitutional repeating units. The different synthesis routes and the various combinations of chiral units result in a multitude of chiral structures and of corresponding properties. Distinctive structural identification is often crucial, especially for applications as degradable polymers. This document provides recommendations for the nomenclature, abbreviations, and terminology related to lactic acid-based polymers in order to allow consistent comparison between polymers of different origins and between data collected within different disciplines.
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Wieczór, Radosław, Arleta Kulwas e Danuta Rość. "Implications of Hemostasis Disorders in Patients with Critical Limb Ischemia—An In-Depth Comparison of Selected Factors". Journal of Clinical Medicine 9, n. 3 (29 febbraio 2020): 659. http://dx.doi.org/10.3390/jcm9030659.
Abstract (sommario):
Background: Atherosclerosis is a systemic disease. Among patients with atherosclerosis, those suffering from peripheral arterial disease (PAD) represent a group of individuals with particularly high death risk, especially during the course of critical limb ischemia (CLI). In the pathogenesis of PAD/CLI complications, blood coagulation disorders play a significant role. The study aim was to examine the activation of the coagulation system depending on tissue factor (TF) in patients with CLI as compared with those with intermittent claudication (IC). Methods: Before initiating proper treatment (invasive or maintenance), blood samples were collected from 65 patients with CLI and 15 with IC to measure the following selected hemostasis parameters: concentrations and activation of tissue factor (TF Ag and TF Act) and tissue factor pathway inhibitor (TFPI Ag and TFPI Act), concentrations of thrombin–antithrombin complex (TAT Ag) and fibrinogen, platelet count (PLT), and concentrations of tissue-plasminogen activator (t-PA Ag), plasminogen activator inhibitor 1 (PAI-1), and D-dimer. The control group included 30 healthy volunteers (10 female/20 male). Results: The values of all analyzed parameters (except for lower TFPI Act) were significantly higher in the blood of PAD patients (with respect to PLT only in the CLI subgroup) in comparison with healthy subjects. The blood of patients with CLI as compared to the IC subgroup revealed much higher concentrations of TF Ag (p < 0.001), with slightly decreased TF Act, significantly lower concentrations of TFPI Ag (p < 0.001), slightly increased TFPI Act, and significantly higher levels of TAT Ag (p < 0.001), fibrinogen (p = 0.026), and D-dimer (p < 0.05). Conclusions: In patients with CLI, we can observe coagulation activation and a shifting balance toward prothrombotic processes. Furthermore, increased concentrations of D-dimer suggest a secondary activation of fibrinolysis and confirm the phenomenon as a prothrombotic condition with heightened fibrinolysis.
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Antaryama, I. Gusti Ngurah. "APPLICABILITY OF DIRECT EVAPORATIVE COOLING FOR LOW-RISE RESIDENTIAL BUILDING IN SURABAYA". DIMENSI (Journal of Architecture and Built Environment) 49, n. 1 (28 luglio 2022): 65–74. http://dx.doi.org/10.9744/dimensi.49.1.65-74.
Abstract (sommario):
Direct evaporative cooling has been widely known as the passive design strategy for ameliorating the thermal conditions of building in hot-dry climates. In the recent past, the strategy has been extended to warm-humid climates. The scope varies from exploring the system to applying the method to buildings. Few studies have been conducted regarding its application on a multi-story residential building. In response to this gap, the present study will explore the strategy's applicability on the typical low-rise housing in Surabaya and analyze its environmental consequences. Simulation is used as the primary method for the analyses. Results of the study show that direct evaporative cooling is applicable in warm-humid tropics, but with some notes regarding the increase of air humidity. Dimensional properties of the cooling pad can be arranged to minimize the increased humidity.
44
Korpela, Antti, Aayush Kumar Jaiswal, Atsushi Tanaka e Jaakko Asikainen. "Wet tensile strength development of PAE wet-strengthened NBSK handsheets by AKD internal sizing". BioResources 17, n. 2 (26 aprile 2022): 3345–54. http://dx.doi.org/10.15376/biores.17.2.3345-3354.
Abstract (sommario):
Polyamide-epichlorohydrin (PAE) is used in papermaking to increase the paper’s wet strength. High levels of PAE can make repulping of paper more difficult. PAE deposits can also impair paper machine performance by plugging the paper machine felts. The results of a preceding study indicated that the wet strength of paper containing a moderate amount of PAE (added amount 0.3 wt%) can be increased by utilizing internal alkylketene dimer (AKD) sizing. In the present study, the effects of an added amount of PAE and AKD on the wet strength of handsheets made from Nordic bleached softwood pulp (NBSK) were examined. The wet strength was measured after soaking the sheets in ion-exchanged water for up to 1 month. The improving effect of AKD sizing on the wet strength was long-lasting and it was apparent especially with a low and moderate added amount of PAE (0.15 and 0.45 wt%) resulting in higher wet strength than the highest added amount of PAE (1.35 wt%) alone. No clear sign of worsened repulpability was observed at low to moderate treatment levels. The results suggest that use of small or moderate amounts of PAE with AKD can be a viable option for paper mills facing problems related to the high usage of PAE.
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Ramaraj, Ramasamy, Akira Kira e Masao Kaneko. "Model oxygen-evolving center composed of polymer membrane and dimer ruthenium complex". Polymers for Advanced Technologies 6, n. 3 (marzo 1995): 131–40. http://dx.doi.org/10.1002/pat.1995.220060306.
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Popov, Evgeny, Jouni Välisaari, Veli-Matti Vuorenpalo, Vesa Hietapelto, Reijo Aksela e Jussi Eloranta. "Stabilization of peracetic acid with aspartic acid diethoxy succinate (AES)". Holzforschung 61, n. 5 (1 agosto 2007): 539–42. http://dx.doi.org/10.1515/hf.2007.104.
Abstract (sommario):
Abstract Stabilization of peracetic acid (PAA) by aspartic acid diethoxy succinate (AES) was studied by electron spin resonance, UV/Vis spectroscopy, electrospray ionization time-of-flight mass spectrometry and oxygen evolution measurements. The results indicate that Mn(II)-AES complexes may exist in both monomeric and dimeric forms. Dimerization is proposed to proceed via formation of an oxygen bridge between two Mn(II)-AES complexes. The equilibrium between these two forms depends strongly on pH, the monomeric form being favored under acidic conditions, while conditions close to neutral pH favor the dimeric form. In the presence of PAA, the dimer form was oxidized and finally yielded MnO2. Oxygen evolution measurements were carried out to demonstrate the efficiency of AES in stabilizing PAA solutions containing small amounts of Mn(II) impurities under acidic conditions.
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Green, David, Yihua Liao, Loyda Vida, Philip Greenland, Mark D. Huffman, Kiang J. Liu, Donald M. Lloyd-Jones et al. "D-Dimer in the Months Leading up to Acute Coronary Events: A Case Crossover Study". Blood 124, n. 21 (6 dicembre 2014): 2864. http://dx.doi.org/10.1182/blood.v124.21.2864.2864.
Abstract (sommario):
Abstract Major coronary events are commonly precipitated by thrombotic occlusion of atheromatous vessels. We determined whether d-dimer, C-reactive protein (CRP), or serum amyloid A (SAA), increase in the months prior to an acute coronary events in patients with severe lower extremity peripheral artery disease (PAD). The Biomarker Risk Assessment in Vulnerable Outpatients (BRAVO) Study enrolled patients with PAD and followed them prospectively every two months. At each visit, participants were queried about new hospitalizations, blood was obtained, electrocardiograms performed, and mortality data collected. Two controls for each patient with events were randomly selected from participants without events, matched for age, sex, race, duration in the study, and number of blood draws. D-dimer was measured using an immunoturbidometric assay (Asserachrom D-Di kit, Diagnostica Stago, Parsippany, NJ). CRP and SAA were determined using an immunotechnique on the Behring BN II analyzer (Dade Behring, Wilmington, DE). Changes in levels of these biomarkers during the months leading up to the primary outcome (acute MI, new MI detected by ECG, hospitalization for unstable angina, cardiac death) were the independent variables of interest. A total of 595 participants with PAD were followed for a mean of 1.56 years; 50 (8.4%) experienced 75 acute coronary events. Sixteen of these cases had five complete visits immediately prior to the event, allowing a comparison of D-dimer levels over time within the same cohort of study participants. Their median/interquartile D-dimer (mg/L, log-transformed) just prior to the event was 1.05 (0.62-1.62); the level was significantly lower at each of the other 4 visits (0.69, 0.71, 0.83, 0.86; all P <0.032 based on paired t-tests). We also compared cases with controls; in 19 cases (36 pairs with controls), D-dimer measurements at the 4 visits leading up to an acute event were significantly higher in the cases than in the controls (Table 1). CRP (mg/L) was increased just prior to events only in comparison with visits at 4 and 8 months (n=16; 3.34 vs 2.29, P=0.03; 3.34 vs 1.94, P=0.02), and was not significantly higher in cases than controls. SAA (mg/L) just prior to an event exceeded only one other value (at 8 months; 0.55 vs 0.37, P=0.02), and was higher in cases than controls at only 1 visit. We conclude that levels of D-dimer are significantly higher within 2 months of an acute coronary event compared to values in the same participants in the months before the event. In addition, D-dimer levels are higher in patients than controls during the 8 month period before an acute coronary event. Levels of CRP and SAA are infrequently increased in patients prior to events and in comparison to those without events. Table 1. Median D-dimer (mg/L) during the 8 months leading up to an ischemic heart disease event. Cases vs Controls No. of pairs/cases Median/Interquartile for case Median/Interquartile for control P-value from GEE* Within 2 months 36/19 1.1 (0.62 to 1.67) 0.53 (0.3 to 0.84) 0.01 4 months 36/19 0.95 (0.52 to 1.55) 0.45 (0.28 to 0.9) 0.03 6 months 36/19 0.83 (0.52 to 1.76) 0.5 (0.27 to 0.91) 0.02 8 months 36/19 0.86 (0.48 to 1.45) 0.48 (0.3 to 0.9) 0.01 *P-value based on the General Estimating Equation (GEE) model using LOG transformed values and assuming correlated error structure Disclosures Huffman: AstraZeneca: Research Funding; Boehringer Ingelheim: Research Funding.
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Śliwa, Marta, Benjamin O. Stephens, Zhe Zhang e Thomas J. Kempa. "Harnessing host–guest interactions to control structure at the nanoscale". Pure and Applied Chemistry 92, n. 12 (16 dicembre 2020): 1895–900. http://dx.doi.org/10.1515/pac-2020-0701.
Abstract (sommario):
AbstractHost–guest interactions mediate many chemical and biochemical transformations and are extensively exploited in a number of industrially-relevant chemical processes. Many porous inorganic (e.g., zeolite) and molecular (e.g., metal-organic framework) hosts engage reagents in their environment through selective host–guest interactions. While researchers frequently capitalize on host–guest interactions to sequester chemical species or to catalyze reactions, these interactions can also be used to direct nanomaterial synthesis. In this Perspective we highlight the promise and opportunities for harnessing host–guest interactions to control the structure and dimensionality of materials. We focus our discussion on emerging strategies in soft chemistry and promising new directions which use porous ionic solids to direct the growth of complex nanoscale dimers and Janus nanoparticles.
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SOUBEYRAND, Sebastien, Claude LAZURE e Puttaswamy MANJUNATH. "Phospholipase A2 from bovine seminal plasma is a platelet-activating factor acetylhydrolase". Biochemical Journal 329, n. 1 (1 gennaio 1998): 41–47. http://dx.doi.org/10.1042/bj3290041.
Abstract (sommario):
The major phospholipase A2 activity from bovine seminal plasma was recently purified [Soubeyrand, Khadir, Brindle and Manjunath (1997) J. Biol. Chem. 272, 222-227]. We here show that the 60 kDa enzyme is in fact a platelet-activating factor acetylhydrolase (PAF-AH). Sequences of the N-terminus as well as of internal fragments showed 100% identity with the cDNA-deduced sequences of bovine plasma PAF-AH. The enzyme has kinetic properties similar to those of the human serum PAF-AH. Although capable of hydrolysing long-chained phosphatidylcholine, it displayed a highly preferential activity towards PAF. The enzyme activity towards phosphatidylcholine, but not PAF, was Ca2+-dependent. Biochemical characterization revealed that the enzyme is extensively N-glycosylated and that it exists predominantly as a dimer in solution. Western blot analysis revealed that the enzyme is highly heterogeneous in charge, with a maximal distribution at an isoelectric point of approx. 5.7. The enzyme was expressed exclusively in the seminal vesicles and the ampulla. No association of the enzyme with either epididymal or ejaculated spermatozoa could be detected.
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Panda, Dr Sibaram, e Dr Sunil Kumar Sharma. "Cardiac evaluation of Covid-19 patients with post-discharge dyspnoea". International Journal of Medical Research & Review 8, n. 6 (23 dicembre 2020): 432–37. http://dx.doi.org/10.17511/ijmrr.2020.i06.11.
Abstract (sommario):
Background: Dyspnoea is one of the common symptoms in COVID-19 patients after discharge fromthe hospital. So evaluation of cardiac function becomes necessary in COVID patients after hospitaldischarge. AIM: To study the cardiac function of COVID 19 patients presenting with dyspnoea afterdischarge from hospital within 3 months of symptom onset. Materials and methods: 245 post-hospital discharge COVID-19 patients enrolled in the study. The patients with abnormalechocardiography are further divided into three groups, A) patients with PAH±RVD, B) patients withLV diastolic dysfunction C) patients with LV systolic dysfunction. Data of the three groups werecompared. Results: Out of 245 patients, 64% (157) patients show abnormal echocardiogram.75(30.6%) patient show PAH±RVD,61(24.8% ) patients shows LV diastolic dysfunction and 21(8.57%)patients shows LV systolic dysfunction. patients with ventricular dysfunction significantly associatedwith multiple risk factors and comorbidity. Grade 1,2,3,4 diastolic dysfunction seen in27.8%,34.4%,29.5%,8.1% in group B respectively. LV systolic dysfunction is mild in 13 (61.9%),moderate in6(28.5%), severe in 1 (4.7 %) in group C patients. Ntprobnp, tropnin significantlyhigher in all groups. Also, CRP, D dimer significantly higher in group A, but non significantly higher ingroup B, C. Conclusion: RV dysfunction is the most common pattern seen in around 30% ofpatients. LV diastolic dysfunction is not uncommon, seen in ¼ the patients. Patients with cardiacdysfunction have a high level of cardiac and inflammatory biomarkers, which can lead to grievouscardiovascular complications. So close follow up required.