4-(α,α-dimethylbenzyl)phenyl methacrylate, 1. Synthesis and crystal structure

4-(α,α-dimethylbenzyl)phenyl methacrylate ( 1 ) was prepared by reaction of 4-(α,α-dimethylbenzyl)phenol and methacryloyl chloride in ether. By careful crystallization from ether large monoclinic crystals could be obtained with the following crystal data: a = 6,622 (2) Å, b = 12,578 (2) Å, c = 9,892 (3) Å, β = 99,86° (3), D_c = 1,147 g · cm^?3, V = 811,1 ų, M = 280,4, λ = 0,7107 Å, μ = (Mo K_α) = 0,7 cm^?1, F(000) = 300, space group P2₁, Z = 2. Attempts to polymerize the monomer (m.p. 46–48°C) by γ-irradiation at ambient temperature gave only a small amount of a crosslinked product.     

4-(α,α-dimethylbenzyl)phenyl methacrylate, 3. Synthesis,tacticity and glass transition temperatures of its polymers

Depending on the kind of initiator, anionic polymerization of 4-(α,α-dimethylbenzyl)phenyl methacrylate in toluene at ?78°C led either to highly isotactic or predominantly syndiotactic polymers as determined by ¹³C NMR spectroscopy. The glass transition temperature difference between the syndiotactic and isotactic polymer appeared to be smaller than in case of poly(alkyl methacrylates), probably because of a larger stiffening effect by the bulky aromatic ester group on the isotactic backbone than on the syndiotactic one.     

Polymerization of α,α-disubstituted β-propiolactones and lactams, 12. Properties and crystalline structure of poly(β-propiolactam)s

A series of α,α-disubstituted β-propiolactams (substituted nylon 3 polymers) was prepared from non-optically active lactams. Their thermal characteristics, densities, and x-ray fiber diffraction patterns were recorded. One of the α-substituents was always a methyl group while the other was either CH₃, C₂H₅, n-C₃H₇, or n-C₄H₉. The melting point for the dimethyl substituted polymer was 268°C; the others were respectively 76, 74, and 72°C. X-ray fiber diffraction data on all four samples yielded the same fiber repeat of ≈8,4 Å. A minimum energy based conformational analysis for the α,α-dimethyl derivative indicates that two conformations correspond to this repeat, each of which is a 2₁ helix.     

Synthesis of New Homopolyester and Copolyesters by Anionic Ring‐opening Polymerization of α,α′,β‐Trisubstituted β‐Lactones

Summary: Novel polyester and copolyesters have been prepared by anionic ring‐opening polymerization of racemic 4‐alkyloxycarbonyl‐3,3‐dimethyl‐2‐oxetanones that had been synthesized in five steps from diethyl oxalpropionate used as chemical precursor. The anionic polymerizations, realized in bulk or in solution with tetraethylammonium benzoate as initiator, led to a homopolymer and copolymers with high molecular weights and polydispersity indices close to unity. These features can be explained by the presence of two methyl groups on the same carbon atom in the lactone, preventing transfer reactions to the monomer. Preparation of seeds and re‐initiation by addition of fresh monomer confirmed a living process. The hydrolysis of poly[(R,S)‐3,3‐dimethylmalic acid] under physiological conditions yielded (R,S)‐3,3‐dimethylmalic acid. A terpolymer was also prepared for biological studies related to its use as biodegradable materials for tissue regeneration.

Structure of poly[(R,S)‐3,3‐dimethylmalic acid].     

Mutarotation of α-D-glucose catalyzed by poly(4-vinylpyridine) and poly(4-vinylpyridinium hydrochloride) in N,N-dimethylformamide solutions

The rate of mutarotation of α-D-glucopyranose catalyzed by polymers of 4-vinylpyridine (4VP) was observed in N,N-dimethylformamide (DMF) solutions. Poly(styrene-co-4VP·HCI) and poly(4VP·HCl) were active while poly(4VP) of various average molecular weights showed little catalytic activity. p-Chlorophenol-poly(4VP) catalyst pair in DMF and poly(4VP·HCl)-poly(4VP) catalyst pair in DMF/methanol mixed solvent showed a catalysis of bifunctional mechanism.     

Polymerizable amphiphiles, 3. Polymerization of micellized 1-O-3-(4-vinylphenyl)propyl-β-D-glucopyranose

1-O-3-(4-Vinylphenyl)propyl-β-D -glucopyranose ( 1 ) was polymerized in organic solvents and in aqueous solutions above and below the critical micelle concentration by three different free-radical initiators: 2,2′-azoisobutyronitrile (AIBN), dipotassium peroxodisulfate (K₂S₂O₈), and 2-(phenylazothio)naphthalene (ATE). The polymerization is self-accelerating in dilute aqueous solutions, regardless of whether oil-soluble or water-soluble initiators were used. Size exclusion chromatography was employed to monitor the change of molar masses, molar mass distributions, and conversions with time. The polymerization kinetics was also followed by UV spectroscopy. The polymerization by ATE led to polymerized micelles (P-mers) under preservation of the degree of micellization. The polymerization by K₂S₂O₈ and AIBN, on the other hand, resulted in the polymerization of bigger micelles (R-mers) beside a small amount of polymerized P-micelles.     

Synthesis of α,ω‐Isocyanate–Telechelic Poly(methyl methacrylate)

The preparation of α,ω‐isocyanate–telechelic poly(methyl methacrylate) using RAFT polymerization and two postpolymerization modification steps is presented. The synthetic strategy includes the RAFT polymerization of methyl methacrylate, which results in a hetero telechelic polymer. In the first modification step by radical exchange, a carboxylic acid homo telechelic PMMA was successfully prepared. Second, the carboxylic acid end groups are reacted with hexamethylene diisocyanate in excess and magnesium chloride as a catalyst. Under mild reaction conditions (80 °C, 4 h), the isocyanate homo telechelic PMMA is obtained. A conversion of 86% of the carboxylic acid end groups was achieved.     

Controlled synthesis of α,β-difunctional poly(hexafluoropropylene oxide)

An improved method is described for the preparation of difunctional poly(hexafluoropropylene oxide) of moderate molecular weight (M _n ≈ 6000) in good yield (>80 wt.-%). With the dependence of chain transfer constant on initiator concentration known, at least under controlled conditions, good molecular-weight control can be achieved.     

C-13-NMR-spektroskopische untersuchungen an polymerhomologen reihen von α,1→6- und α,1→4-glucanen

The ¹³C-NMR spectra of malto- and isomalto-oligosaccharides, amylose and dextrane were analysed. It was observed that in both series of oligosaccharides and polysaccharides the resonances of the central glucose units are independent of the chain length with the exception of the C-atoms 1 and 4 of amylose which show deviations of 0,4 and 0,5 ppm. These small effects can possibly be explained by a definite polysaccharide chain conformation in solution.     

T-CELL RECEPTOR α, δ, AND γ CHAIN GENES IN INSULIN-DEPENDENT DIABETES MELLITUS

We have studied the genotypic, haplotypic, and allelic distribution of germline Restriction Fragment Length Polymorphism (RFLP) of T-cell receptor (Tcr) α, γ, and δ loci in 75 insulin-dependent diabetes mellitus (IDDM) patients and 84 healthy blood donors as control population. The restriction endonuclease PvuII produces three allelic fragments of Tcr C-γ (TcrCG) gene segment of 16,13, and 11.3 Kb respectively. Our observations revealed that PvuII/TcrCG RFLP allelic distributions were not significantly different in the IDDM and the control group. However, 85% of IDDM patients carried HLA DR3 and/or DR4 haplotypes, and when comparing these patients with a second group of HLA DR3+ and/or DR4+ healthy individuals, the 11Kb/PvuII fragment of TcrCG gene was found to be associated with IDDM patients (χ= 11.4, P= 0.003). 54.9% of IDDM patients carried at least one 11.3 Kb allele vs. 21% in controls (χ= 10.77, P = 0.004). No significant association was found between RFLP in Tcr, Cα, Cδ, Vγ9 loci and IDDM.     

Polymerization of methyl methacrylate in the presence of poly(α-amino acid)s

The polymerization of methyl methacrylate (MMA) was studied in the presence of poly(α-amino acid)s, water, and copper(II) ion. It was found that the polymerization behaviour depends very much on the conformation of the poly(α-amino acid) in the system. If the poly(α-amino acid) had the α-helix conformation, the polymerization of MMA did not occur. This is supposed to be due to the stability of the intramolecular hydrogen bond in the α-helix, which is too high to form a chelate complex between the copper ion and the polypeptide together with the MMA monomer and water. When the same polypeptides took a random coil conformation, however, the polymerization occurred, although to a small extent. Furthermore, when the polypeptide with the β-conformation was used, the polymerization of MMA occured to a higher extent than in the case of the polypeptide with the random coil conformation. Therefore, it was concluded that the delocalization of electrons in the copper ion to the neighbouring atoms plays an important rǒle in the initiation of the polymerization of MMA. It was also found that the size of the nonpolar side chain of the initiating polypeptides affects the polymerization of MMA. Since this polymerization is carried out in water, the hydrophobic bonds between the nonpolar side chain of the polypeptide and the MMA monomer may also play an important rǒle.     

The production of 3aα-H-4α-(3′-propionic acid)-5α-hydroxy-7aβ-methylhexahydro-1-indanone-δ-lactone by Nocardia restricta mutants

Two mutants of Nocardia restricta breakdown androst-4-ene-3,17-dione into 3aα-H-4α-(3′-propionic acid)-5α-hydroxy-7aβ-methylhexahydro-l-indanone-δ-lactone. The metabolic intermediates formed are very different in each mutant. One uses certain aromatic compounds very slowly. A degradation pathway for steroids by Nocardia restricta has been proposed.     

Localization of phosphatidylinositol 4‐phosphate 5‐kinase (PIP5K) α, β, γ in the three major salivary glands in situ of mice and their response to β‐adrenoceptor stimulation

Phosphatidylinositol 4‐phosphate 5‐kinase (PIP5K), which is composed of three isozymes (α, β and γ), catalyzes the production of phosphatidylinositol bisphosphate (PIP2). This phospholipid functions in membrane trafficking, as an anchor for actin cytoskeletons and as a regulator of intramembranous channels/transporters. It is also a precursor of such second messengers as diacylglycerol, inositol triphosphate and phosphatidylinositol (3,4,5)‐triphosphate. In the present study, the expression and localization of endogenous PIP5Ks were examined in the three major salivary glands of young adult mice in situ. In western blotting of normal control glands, immunoreactive bands for individual PIP5Ks were detectable, with the highest density in the parotid gland and the weakest density in the submandibular gland. In immuno‐light microscopy under non‐stimulated condition, weak immunoreactivity for PIP5Kα was confined to the apical plasmalemma in parotid, but not sublingual or submandibular, acinar cells. Immunoreactivity for PIP5Kβ was weak to moderate and confined to ductal cells but not acinar cells, whereas that for PIP5Kγ was selectively and intensely detected in myoepithelial cells but not acinar cells, and it was weak in ductal cells in the three glands. In western blot of the parotid gland stimulated by isoproterenol, a β‐adrenoceptor agonist, no changes were seen in the intensity of immunoreactive bands for any of the PIP5Ks. In contrast, in immuno‐light microscopy, the apical immunoreactivity for PIP5Kα in parotid acinar cells was transiently and distinctly increased after the stimulation. The increased immunoreactivity was ultrastructurally localized on most apical microvilli and along contiguous plasma membrane, where membranous invaginations of various shapes and small vesicles were frequently found. It was thus suggested that PIP5Kα is involved in post‐exocytotic membrane dynamics via microvillous membranes. The present finding further suggests that each of the three isoforms of PIP5K functions through its product PIP2 discretely in different cells of the glands to regulate saliva secretion.     

Atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate with α,α‐dichlorotoluene as initiator; a kinetic study

The atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate with α,α‐dichlorotoluene ( DCT ) as initiator results in the respective chlorotelechelic polymers. From a kinetic point of view, however, the polymerization of styrene and methyl methacrylate show a different behavior: for the polymerization of styrene DCT is a bifunctional, for the polymerization of methyl methacrylate it is a monofunctional initiator.     

Detection of Intimins α, β, γ, and δ, Four Intimin Derivatives Expressed by Attaching and Effacing Microbial Pathogens

Intimins are outer membrane proteins expressed by enteric bacterial pathogens capable of inducing intestinal attachment-and-effacement lesions. A eukaryotic cell-binding domain is located within a 280-amino-acid (Int280) carboxy terminus of intimin polypeptides. Polyclonal antiserum was raised against Int280 from enteropathogenic Escherichia coli (EPEC) serotypes O127:H6 and O114:H2 (anti-Int280-H6 and anti-Int280-H2, respectively), and Western blot analysis was used to explore the immunological relationship between the intimin polypeptides expressed by different clinical EPEC and enterohemorrhagic E. coli (EHEC) isolates, a rabbit diarrheagenic E. coli strain (RDEC-1), and Citrobacter rodentium. Anti-Int280-H6 serum reacted strongly with some EPEC serotypes, whereas anti-Int280-H2 serum reacted strongly with strains belonging to different EPEC and EHEC serotypes, RDEC-1, and C. rodentium. These observations were confirmed by using purified Int280 in an enzyme-linked immunosorbent assay and by immunogold and immunofluorescence labelling of whole bacterial cells. Some bacterial strains were recognized poorly by either antiserum (e.g., EPEC O86:H34 and EHEC O157:H7). By using PCR primers designed on the basis of the intimin-encoding eae gene sequences of serotype O127:H6, O114:H2, and O86:H34 EPEC and serotype O157:H7 EHEC, we could distinguish between different eae gene derivatives. Accordingly, the different intimin types were designated α, β, δ, and γ, respectively.     

An immunohistochemical examination of the expression of E-cadherin, α- and β/γ-catenins,and α2- and β1-integrins in invasive breast cancer

This study examines the expression of the cell–cell adhesion molecules E-cadherin and its associated proteins, the catenins and the matrix–cell adhesion molecules β1- and α2-integrins, in primary invasive breast carcinoma. Expression was assessed immunohistochemically on frozen sections by semi-quantitative scoring of the intensity and proportion of immunoreactivity in 55 cases. Associations with each other and with other histological and prognostic features and survival were sought. There was a significant association between loss of E-cadherin expression and loss of α- and β/γ-catenin immunostaining. In 20 per cent of cases, membranous immunoreactivity with E-cadherin antibody was absent. Absent cytoplasmic expression of α- and β/γ-catenins was seen in 24 and 22 per cent of breast cancers, respectively. The intensity of reactivity with E-cadherin showed a significant association with histological grade (p = 0·002) and tumour type (p < 0·001). Lobular carcinomas frequently showed loss of expression of E-cadherin, as reported elsewhere; loss of catenin expression was also found in these tumours. α-Catenin intensity also showed a relationship with grade (p = 0·008) and with oestrogen receptor (ER) status (p = 0·006). β/γ-Catenin expression was not associated with other known prognostic factors. Forty-nine per cent and 42 per cent of cases showed no membrane immunostaining with β1- and α2-integrin, respectively, and co-ordinated loss of β1- and α2-integrin expression was found. Both β1- and α2-integrin expression were associated with histological grade (p = 0·003 and p = 0·031, respectively) and β1 immunoreactivity with tumour type (p = 0·010). None of the variables examined showed a statistically significant association with tumour size or lymph node stage, or with overall survival, although a trend was seen (p = 0·087) towards poorer survival of patients with tumours with absent or weak expression of β1-integrin. The expression of these markers is of biological interest, but appears to be of little additional use in predicting clinical behaviour. Copyright © 1999 John Wiley & Sons, Ltd.     

Rapsyn interacts with the muscle acetylcholine receptor via α-helical domains in the α, β, and ε subunit intracellular loops

At the developing vertebrate neuromuscular junction, the acetylcholine receptor becomes aggregated at high density in the postsynaptic muscle membrane. Receptor localization is regulated by the motoneuron-derived factor, agrin, and requires an intracellular, scaffolding protein called rapsyn. However, it remains unclear where rapsyn binds on the acetylcholine receptor and how their interaction is regulated. In this study, we identified rapsyn's binding site on the acetylcholine receptor using chimeric constructs where the intracellular domain of CD4 was substituted for the major intracellular loop of each mouse acetylcholine receptor subunit. When expressed in heterologous cells, we found that rapsyn clustered and cytoskeletally anchored CD4-α, β and ε subunit loops but not CD4-δ loop. Rapsyn-mediated clustering and anchoring was highest for β loop, followed by ε and α, suggesting that rapsyn interacts with the loops with different affinities. Moreover, by making deletions within the β subunit intracellular loop, we show that rapsyn interacts with the α-helical region, a secondary structural motif present in the carboxyl terminal portion of the subunit loops. When expressed in muscle cells, rapsyn co-immunoprecipitated together with a CD4-α helical region chimera, independent of agrin signaling. Together, these findings demonstrate that rapsyn interacts with the acetylcholine receptor via an α-helical structural motif conserved between the α, β and ε subunits. Binding at this site likely mediates the critical rapsyn interaction involved in localizing the acetylcholine receptor at the neuromuscular junction.     

Structural analyses of poly(m-xylene-α,α′-diyladipamide) and nylon 66 by 15N solid state NMR

¹⁵N solid state NMR, viz. both ¹⁵N cross polarization (CP) NMR and ¹⁵N CP/magic angle spinning (MAS) NMR, is applied to the structural determination—including molecular orientation—of uniaxially oriented poly(m-xylene-α,α′-diyladipamide) film and nylon 66 fiber on the basis of the chemical shift tensors. In the spectrum of a poly(m-xylene-α,α′-diyladipamide) block sample whose fiber axis was set up parallel to the applied magnetic field, a single main peak with 20% powder pattern (non-crystalline domains) was observed. The small difference in the structure of the main chain between these two uniaxially stretched polyamides was clarified from the chemical shift data of the parallel spectra which reflect the angle between the NH bond and the fiber axis. Determinations of the angles between various molecular-fixed axes and the axis of polymer alignment were tried.