Evidence for stereoregulations in the polymerisation of phenylsilane by bis (indenyl)dimethylzirconium complexes

1990 ◽  
Vol 68 (9) ◽  
pp. 1638-1640 ◽  
Author(s):  
F. Gauvin ◽  
J. F. Harrod
Keyword(s):  
Molecular Weight ◽  
Nmr Spectra ◽  
Low Molecular Weight ◽  
H Nmr ◽  
Zirconium Complexes

Bis(indenyl)dimethylzirconocene, 1, and [1,2-bis(indenyl)ethane]dimethylzirconocene, 2, both catalyze the dehydropolymerization of phenylsilane to a mixture of low molecular weight cyclic oligosilanes (PhSiH)n (n = 6–9). The limited number of sharp resonances in the 29Si and 1H NMR spectra of the polymer produced with 2 as catalyst indicates that the catalyst exerts a significant stereoregulating influence on the polymerization. Keywords: polysilanes, catalytic dehydrocoupling, stereoregulation, bis(indenyl)zirconium complexes.

Combined proteomic and metabonomic studies in three genetic forms of the renal Fanconi syndrome

2007 ◽  
Vol 293 (2) ◽  
pp. F456-F467 ◽  
Author(s):  
Annalisa Vilasi ◽  
Pedro R. Cutillas ◽  
Anthony D. Maher ◽  
Severine F. M. Zirah ◽  
Giovambattista Capasso ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Fanconi Syndrome ◽  
Low Molecular Weight ◽  
Renal Fanconi Syndrome ◽  
Dent’S Disease ◽  
H Nmr ◽  
Low Molecular Weight Proteinuria ◽  
Dent's Disease ◽  
Underlying Mechanisms ◽  
Normal Urine

The renal Fanconi syndrome is a defect of proximal tubular function causing aminoaciduria and low-molecular-weight proteinuria. Dent's disease and Lowe syndrome are defined X-linked forms of Fanconi syndrome; there is also an autosomal dominant idiopathic form (ADIF), phenotypically similar to Dent's disease though its gene defect is still unknown. To assess whether their respective gene products are ultimately involved in a common reabsorptive pathway for proteins and low-molecular-mass endogenous metabolites, we compared renal Fanconi urinary proteomes and metabonomes with normal (control) urine using mass spectrometry and1H-NMR spectroscopy, respectively. Urine from patients with low-molecular-weight proteinuria secondary to ifosfamide treatment (tubular proteinuria; TP) was also analyzed for comparison. All four of the disorders studied had characteristic proteomic and metabonomic profiles. Uromodulin was the most abundant protein in normal urine, whereas Fanconi urine was dominated by albumin.1H-NMR spectroscopic data showed differences in the metabolic profiles of Fanconi urine vs. normal urine, due mainly to aminoaciduria. There were differences in the urinary metabolite and protein compositions between the three genetic forms of Fanconi syndrome: cluster analysis grouped the Lowe and Dent's urinary proteomes and metabonomes together, whereas ADIF and TP clustered together separately. Our findings demonstrate a distinctive “polypeptide and metabolite fingerprint” that can characterize the renal Fanconi syndrome; they also suggest that more subtle and cause-specific differences may exist between the different forms of Fanconi syndrome that might provide novel insights into the underlying mechanisms and cellular pathways affected.

scholarly journals Structure Analysis and Anti-Tumor and Anti-Angiogenic Activities of Sulfated Galactofucan Extracted from Sargassum thunbergii

Marine Drugs ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 52 ◽  
Author(s):  
Weihua Jin ◽  
Wanli Wu ◽  
Hong Tang ◽  
Bin Wei ◽  
Hong Wang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Structure Analysis ◽  
Nmr Spectra ◽  
Low Molecular Weight ◽  
Gel Chromatography ◽  
Sargassum Thunbergii ◽  
Sulfation Pattern ◽  
Fucose Content

Sulfated galactofucan (ST-2) was obtained from Sargassum thunbergii. It was then desulfated to obtain ST-2-DS, and autohydrolyzed and precipitated by ethanol to obtain the supernatant (ST-2-S) and precipitate (ST-2-C). ST-2-C was further fractionated by gel chromatography into two fractions, ST-2-H (high molecular weight) and ST-2-L (low molecular weight). Mass spectrometry (MS) of ST-2-DS was performed to elucidate the backbone of ST-2. It was shown that ST-2-DS contained a backbone of alternating galactopyranose residues (Gal)n (n ≤ 3) and fucopyranose residues (Fuc)n. In addition, ST-2-S was also determined by MS to elucidate the branches of ST-2. It was suggested that sulfated fuco-oligomers might be the branches of ST-2. Compared to the NMR spectra of ST-2-H, the spectra of ST-2-L was more recognizable. It was shown that ST-2-L contain a backbone of (Gal)n and (Fuc)n, sulfated mainly at C4 of Fuc, and interspersed with galactose (the linkages were likely to be 1→2 and 1→6). Therefore, ST-2 might contain a backbone of (Gal)n (n ≤ 3) and (Fuc)n. The sulfation pattern was mainly at C4 of fucopyranose and partially at C4 of galactopyranose, and the branches were mainly sulfated fuco-oligomers. Finally, the anti-tumor and anti-angiogenic activities of ST-2 and its derivates were determined. It was shown that the low molecular-weight sulfated galactofucan, with higher fucose content, had better anti-angiogenic and anti-tumor activities.

Structural features of low-molecular-weight heparins affecting their affinity to antithrombin

2009 ◽  
Vol 102 (11) ◽  
pp. 865-873 ◽  
Author(s):  
Antonella Bisio ◽  
Davide Vecchietti ◽  
Laura Citterio ◽  
Marco Guerrini ◽  
Rahul Raman ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Nmr Spectra ◽  
Biological Activities ◽  
Anticoagulant Activity ◽  
2D Nmr ◽  
Structural Features ◽  
Size Exclusion ◽  
Low Molecular Weight ◽  
Low Molecular Weight Heparins ◽  
2D Nmr Spectra

SummaryAs part of a more extensive investigation on structural features of different low-molecular-weight heparins (LMWHs) that can affect their biological activities, Enoxaparin,Tinzaparin and Dalteparin were characterised with regards to the distribution of different chain length oligosaccharides as determined by size-exclusion (SE) chromatography, as well as their structure as defined by 2D-NMR spectra (HSQC). The three LMWHs were also fractionated into high affinity (HA) and no affinity (NA) pools with regards to their ability to bind antithrombin (AT).The HA fractions were further subfractionated and characterised. For the parent LMWHs and selected fractions,molecular weight parameters were measured using a SE chromatographic system with a triple detector (TDA) to obtain absolute molecular weights. The SE chromatograms clearly indicate that Enoxaparin is consistently richer in shorter oligosaccharides than Tinzaparin and Dalteparin. Besides providing the content of terminal groups and individual glucosamine and uronic acid residues with different sulfate substituents, the HSQC-NMR spectra permitted us to evaluate and correlate the content of the pentasaccharide, AT-binding sequence A-G-A*-I-A (AT-bs) through quantification of signals of the disaccharide sequence G-A*.Whereas the percent content of HA species is approximately the same for the three LMWHs, substantial differences were observed for the chain distribution of AT-bs as a function of length, with the AT-bs being preferentially contained in the longest chains of each LMWH. The above information will be useful in establishing structure-activity relationships currently under way. This study is therefore critical for establishing correlations between structural features of LMWHs and their AT-mediated anticoagulant activity.

Structure of sodium tetracaprolactamatoaluminate. 1H NMR spectra of sodium isobutylcaprolactamatoaluminates

1983 ◽  
Vol 48 (10) ◽  
pp. 2728-2734 ◽  
Author(s):  
Otomar Kříž ◽  
Jiří Fusek ◽  
Bohuslav Čásenský
Keyword(s):  
Molecular Weight ◽  
1H Nmr ◽  
Nmr Spectra ◽  
Benzene Solution ◽  
Sodium Atom ◽  
1H Nmr Spectra ◽  
H Nmr

Sodium tetracaprolactamatoaluminate (I) exists in benzene solution predominantly as a dimer. Its structure was proposed on the basis of molecular weight studies, infrared, and 1H NMR spectra of sodium isobutylcaprolactamatoaluminates (II). Two modes of dimerization are supposed: an eight-membered cyclic caprolactam bridge between two aluminum atoms or the coordination of the caprolactam ligands belonging to two different aluminum atoms to one sodium atom.

Copolymerization of 5-norbornene-2-metheneoxy-trimethylsilyl with methyl 5-norbornene-2-carboxylate catalyzed by a novel Ni(benzocyclohexan-ketonaphthylimino)2/B(C6F5)3) system

2012 ◽  
Vol 32 (6-7) ◽  
pp. 415-423
Author(s):  
Xiaofeng Wang ◽  
Xiaohui He ◽  
Defu Chen ◽  
Yiwang Chen
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Nmr Spectra ◽  
Catalyst System ◽  
Narrow Molecular Weight Distribution ◽  
Complex Catalyst ◽  
Good Thermal Stability ◽  
H Nmr ◽  
Catalyst Systems ◽  
C Nmr

Abstract Copolymerization of 5-norbornene-2-metheneoxy-trimethylsilyl [NB-CH2OSi(CH3)3] with norbornene (NB) or methyl 5-norbornene-2-carboxylate (NB-COOCH3) was carried out in toluene by using novel nickel(II) complex catalyst systems, Ni(benzocyclohexan-ketonaphthylimino)2/B(C6F5)3 [Ni(bchkni)2/B(C6F5)3]. The catalyst system showed high activity on the copolymerization of NB-CH2OSi(CH3)3 with NB (2.3–3.3×104 gpolymer/molNi·h) and NB-CH2OSi(CH3)3 with NB-COOCH3(0.5–3.0×104 gpolymer/molNi·h). However, the solubility of copolymers of NB-CH2OSi(CH3)3 with NB and NB-CH2OSi(CH3)3 with NB-COOCH3, which contain 18.7–86.7 mol% of NB-CH2OSi(CH3)3, was too poor to characterize. The achieved copolymers were confirmed to be vinyl-addition copolymers through the analysis of FTIR, 1H NMR, and 13C NMR spectra. The incorporation rate was 8.7–86.7 mol% at a content of 10–90 mol% of the NB-CH2OSi(CH3)3 in the monomer feeds ratios. The obtained ester functionalized NB copolymer containing 8.7–18.7 mol% of NB-CH2OSi(CH3)3 showed a moderate molecular weight (Mw=1.6–6.0×104 g/mol) and relative narrow molecular weight distribution (Mw/Mn=1.6–2.2). Thermogravimetry (TGA) analyses results showed that the copolymers exhibited good thermal stability (Td=330–350°C) and were noncrystalline by WAXD analyses results.

Zirconium Complexes Having Phenoxy/Cycloalkylimine Chelate Ligands for the Polymerization of Ethylene for Vinyl-Terminated Low Molecular Weight Polyethylenes

2002 ◽  
Vol 31 (7) ◽  
pp. 740-741 ◽  
Author(s):  
Sei-ichi Ishii ◽  
Makoto Mitani ◽  
Junji Saito ◽  
Sadahiko Matsuura ◽  
Shin-ichi Kojoh ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight ◽  
Zirconium Complexes ◽  
Chelate Ligands

1: 13- und 1: 14-Heteropolyvanadate des Phosphors(V) / 1:13- and 1:14- Heteropolyvanadates of Phosphorus(V)

1976 ◽  
Vol 31 (12) ◽  
pp. 1585-1591 ◽  
Author(s):  
Fritz Preuss ◽  
Heinrich Schug
Keyword(s):  
Molecular Weight ◽  
Nmr Spectra ◽  
Soluble Salts ◽  
Oh Groups ◽  
H Nmr ◽  
Stable Species ◽  
Wide Range ◽  
Wide Line

Deep red heteropolyvanadates of phosphorus(V) n M2O:P2O5: 13 V2O5 · aq (n = 3, 5, 6; M = Na, K, Rb, Cs, NH4) and n M2O: P2O5: 14 V2O5 · aq (n = 4, 7; M = K, Rb, Cs, NH4, (n-C4H9)4N) were prepared. Recrystallization of 1: 13- and 1: 14-heteropolyvanadates and determination of molecular weight by ultracentrifuge technique in solutions from V2O5 and NaH2PO4 indicate 1: 14-heteropolyvanadate ions to be stable species over a wide range of pH, while 1: 13-heteropolyvanadate ions are only stabilized in higher acidified solutions containing H2PO4- or as slightly soluble salts. Wide line 1H NMR spectra are interpreted in terms of OH groups and H2O of cristallization, the isolated heteropolyvanadates of both series consisting of protonated anions; the basicity of heteropolyvanadic acids of phosphorus(V) is unknown.

scholarly journals Inferences on the Nature of a Cr(V) or Cr(IV) Species Formed by Reduction of Dichromate by a Bovine Liver Homogenate: NMR and Mass-Spectrometric Studies

2003 ◽  
Vol 1 (3-4) ◽  
pp. 285-298 ◽  
Author(s):  
Elena Gaggelli ◽  
Nicola D'Amelio ◽  
Nicola Gaggelli ◽  
Gianni Valensin ◽  
Lucia Bovalini ◽  
...  
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Diffusion Coefficient ◽  
Liver Homogenate ◽  
Bovine Liver ◽  
Mass Spectrometric ◽  
Low Molecular Weight ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Molecular Masses

A low-molecular weight chromium-containing fraction of the material resulting from dichromate reduction by bovine liver homogenate was investigated by NMR and ES-MS. The ES-MS spectrum showed a readily detectable peak at m/z = 786.1. The same molecular weight reasonably agreed with the relatively low diffusion coefficient measured by NMR-DOSY experiments on the main species observed in the1H NMR spectrum. At least two downfield shifted and broad paramagnetic signals were apparent in the1H NMR spectrum. Temperature dependence of chemical shift was exploited in order to estimate the diamagnetic shift of the signals in the diamagnetic region of the spectrum. 2D TOCSY, NOESY, COSY and1H-3C HMQC spectra revealed the presence of aromatic protons (which were assigned as His residues), Gly and some other short chain amino-acids. Combinations of the molecular masses of such components together with acetate (which is present in the solution) and chromium atoms allowed a tentative proposal of a model for the compound.

Fractionation of soluble portion of reductively alkylated bituminous coals

1986 ◽  
Vol 51 (5) ◽  
pp. 1071-1082 ◽  
Author(s):  
Maya D. Stefanova ◽  
Ivo Lang
Keyword(s):  
Molecular Weight ◽  
Thin Layer ◽  
Elemental Composition ◽  
Silica Gel ◽  
Nmr Spectra ◽  
Benzene Solution ◽  
Polar Compounds ◽  
H Nmr ◽  
Hcl Gas ◽  
Bituminous Coals

Five bituminous coals were reductively alkylated with potassium and 1-butyl iodide in THF. The benzene soluble portion of reductively butylated coals were separated into the saturates, aromatics, neutral heterocyclics, ethers and polar compounds on a silica gel column. From the saturates, the n-alkanes were isolated by the thin-layer and column chromatography on silica gel, and then analyzed by GC. The aromatics were fractionated on a dual packed SiO2/Al2O3 column. The mono- and diaromatic fractions obtained were studied by GC-MS method. The non-hydrocarbon and polar compounds were charcterized by elemental composition, VPO molecular weight and both IR and 1H NMR spectra. The asphaltenes from one reductively butylated coal were fractionated into basic and acidic/neutral parts after bubbling dry HCl gas through their benzene solution. A concept that benzene eluates collect C-alkylation products and diethyl ether + THF mixtures collect the products of O-alkylation was evolved. The ratio of C-alkylation to O-alkylation was found to be a function of the C content of the initial coals.

scholarly journals Fast and Convenient Synthesis of Amine-Terminated Polylactide as a Macroinitiator forω-Benzyloxycarbonyl-L-Lysine-N-Carboxyanhydrides

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Mingjie Ju ◽  
Feirong Gong ◽  
Shujun Cheng ◽  
Yun Gao
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Low Molecular Weight ◽  
Amine Group ◽  
H Nmr ◽  
Convenient Synthesis ◽  
Ft Ir ◽  
Chain Lengths

Amine-terminated poly (L-lactide) (NH2-PLLA) with various chain lengths were successfully synthesized by sequential tert-butyl-N-(3-hydroxypropyl) carbamate initiated bulk ring-opening polymerization (ROP) of L-lactide (L-LA) in the presence of Stannous(II) 2-ethylhexanoate (Sn(Oct)2) and deprotection of theN-tert-butoxycarbonyl (Boc) group at the end of the polymer chain. The polymers obtained were characterized by FT-IR,1H NMR, and GPC method. NH2-PLLA thus prepared was used to initiate the polymerization of ω-benzyloxycarbonyl-L-lysine-N-carboxyanhydride (Lys (Z)-NCA), and the result confirmed the high nucleophilicity of the terminal amine group. This method was not only suitable for the preparation of low molecular weight NH2-PLLA, but also quite efficient in the synthesis of high molecular weight samples.

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