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The temperature dependence of the tilt angle in the smectic C phase has been determined using a novel method based on dielectric absorption measurements in the smectic A and C phases, of both chiral and non-chiral compounds. The appropriate expressions for evaluating this tilt angle θ from dielectric absorption spectra are derived. The critical exponent for the tilt angle obtained by the dielectric method was found to be in good agreement with results from optical methods.

Ferroelectric liquid crystalline phases formed by achiral bent-core mesogens have been known for about seven years. However, only few materials have been found to exhibit both conventional nematicsmectic mesophases and “banana” phases, where steric packing of bent mesogens results in ferroelectric properties. In this paper we report some studies of such compounds showing transitions between paraelectric smectic A, smectic C and antiferroelectric smectic CP phases. Structure characterization as well as studies of ordering in mesophases have been performed with the help of a variety of experimental techniques including X-ray diffraction, NMR and dielectric spectroscopy as well as electrooptical measurements.

Decorin, a small multifunctional proteoglycan, has been shown to be causally involved in the formation of capillary-like structures and a decrease in apoptosis. Here we investigated signal transduction pathways mediating effects of decorin on endothelial cells (ECs). Addition of decorin led to a fourfold increase in phosphorylation of Aktprotein kinase B on Thr307 and a l.4-fold increase on Ser473 after 10 min, but this phosphorylation could not be blocked by preincubation with Ly29400 (10 ?M). Six hours after the addition of decorin, the synthesis of p21 and p27, two inhibitors of cyclin-dependent kinases, started and increased up to 18 h, while synthesis of cyclin A peaked at 12 h and decreased after 24 h below base level. Induction of dominan-negative Akt by a replication-deficient adenovirus blocked p21 and cyclin A synthesis, but had no effect on p27. Dominant-negative Akt also blocked the antiapoptotic effect of decorin on ECs, but induction of dominant-positive Akt could not rescue the cells from apoptosis. Thus, the matrix proteoglycan decorin is a signaling molecule in ECs that affects cell survival by Akt-dependent and -independent pathways.

ObjectiveDisturbances in proteoglycan metabolism of hyaline cartilage play an essential role in the pathology of degenerative joint disease. We investigated the relation between transcript expression, protein synthesis and the ultrastructural localization of the matrix-organizing proteoglycans decorin and biglycan within intra- and extracellular compartments of late-stage osteoarthritic human articular cartilage.

Biglycan is a member of the small leucine-rich proteoglycan family. Its core protein comprises two chondroitin/dermatan sulfate attachment sites on serine 42 and serine 47, respectively, which are the fifth and tenth amino acid residues, respectively, after removal of the prepro peptide. Because the regulation of glycosaminoglycan chain assembly is not fully understood and because of the in vivo existence of monoglycanated biglycan, mutant core proteins were stably expressed in human 293 and Chinese hamster ovary cells in which i) either one or both serine residues were converted into alanine or threonine residues, ii) the number of acidic amino acids N-terminal of the respective serine residues was altered, and iii) a hexapeptide was inserted between the mutated site 1 and the unaltered site 2. Labeling experiments with [(35)S]sulfate and [(35)S]methionine indicated that serine 42 was almost fully used as the glycosaminoglycan attachment site regardless of whether site 2 was available or not for chain assembly. In contrast, substitution of site 2 was greatly influenced by the presence or absence of serine 42, although additional mutations demonstrated a direct influence of the amino acid sequence between the two sites. When site 2 was not substituted with a glycosaminoglycan chain, there was also no assembly of the linkage region. These results indicate that xylosyltransferase is the rate-limiting enzyme in glycosaminoglycan chain assembly and implicate a cooperative effect on the xylosyl transfer to site 2 by xylosylation of site 1, which probably becomes manifest before the removal of the propeptide. It is shown additionally that biglycan expressed in 293 cells may still contain the propeptide sequence and may carry heparan sulfate chains as well as sulfated N-linked oligosaccharides.

Cell surface-associated heparan sulfate proteoglycans, predominantly perlecan, are involved in the process of binding and endocytosis of thrombospondin-1 (TSP-1) by vascular endothelial cells. To investigate the structural properties of heparan sulfate (HS) side chains that mediate this interaction, the proteoglycans were isolated from porcine endothelial cells and HS chains obtained thereof by beta-elimination. To characterize the structural composition of the HS chains and to identify the TSP-1-binding sequences, HS was disintegrated by specific chemical and enzymatic treatments. Cell layer-derived HS chains revealed the typical structural heterogeneity with domains of non-contiguously arranged highly sulfated disaccharides separated by extended sequences containing predominantly N-acetylated sequences of low sulfation. Affinity chromatography on immobilized TSP-1 demonstrated that nearly all intact HS chains possessed binding affinity, whereas after heparinase III treatment only a small proportion of oligosaccharides were bound with similar affinity to the column. Size fractioning of the bound and unbound oligosaccharides revealed that only a specific portion of deca- to tetradecasaccharides possessed TSP-1-binding affinity. The binding fraction contained over 40% di- and trisulfated disaccharide units and was enriched in the content of the trisulfated 2-O-sulfated L-iduronic acid-N-sulfated-6-O-sulfated glucosamine disaccharide unit. Comparison with the disaccharide composition of the intact HS chains and competition experiments with modified heparin species indicated the specific importance of N- and 6-O-sulfated glucosamine residues for binding. Further depolymerization of the binding oligosaccharides revealed that the glucosamine residues within the TSP-1-binding sequences are not continuously N-sulfated. The present findings implicate specific structural properties for the HS domain involved in TSP-1 binding and indicate that they are distinct from the binding sequence described for basic fibroblast growth factor, another HS ligand and a potential antagonist of TSP-1.

AbstractThe structure of aerosil in a liquid crystal was investigated by atomic force microscopy. Depending on the preparation of the sample different agglomerates of aerosil in the liquid crystalline matrix were detected.

AbstractBinary systems of 1-heptyl-4-(4-pyridyl)pyridinium bromide with different proton acceptors were investigated. The existence of hydrogen bonded liquid-crystalline associates was proven.

AbstractThe phase behavior of ceramides IV, the rigid palmitic acid, the fluid oleic acid and the fluid α-methyl palmitic acid in pure and mixed monolayers at the air/water interface is reported. Like natural oleic acid the synthesized α-methyl palmitic acid forms fluid-expanded films, but they are stable with time. All described mixtures were transferred to hydrophilic surface of a Si-wafer as z-type Langmuir-Blodgett monolayers. The surface morphology of these layers is characterized by atomic force microscopy (AFM). It could be shown that addition of all three fatty acids to ceramides IV changes the morphological properties of the film.

AbstractTerminally alkyl- and alkyloxysubstituted 4,6-dichloro-1,3-phenylene bis[4-(phenyliminomethyl)benzoates] have been synthesized and studied by optical microscopy, differential scanning calorimetry, NMR spectroscopy, X-ray diffraction and dielectric measurements. Surprisingly, nematic and smectic phases are observed, although comparable bisesters of resorcinol and monochlororesorcinol exhibit B phases typical for banana-shaped mesogens. It could be proved by NMR investigations in the liquid crystallinen state that the molecules have a nearly rod-like shape. Dielectric measurements indicate a rotation around the molecular long axis as known from calamitic mesogens, which is clearly distinguished from the behaviour of bent molecules. Obviously, substitution of the central phenyl ring of the bent 1,3-phenylene bis[4(4-n-alkyloxyphenyliminomethyl)benzoates] by two chlorine atomas causes a markedly change of the molecular shape resulting in nearly calamitic mesogens. These results are supported by single crystal structure studies, which allow the precise determination of the molecular structure and packing in the solid state.

AbstractDielectric investigations of two diols with different molecular shape are carried out in the MHz-range and discussed.

A seventh member of the human beta4-galactosyltransferase family, beta4Gal-T7, was identified by BLAST analysis of expressed sequence tags. The coding region of beta4Gal-T7 depicts a type II transmembrane protein with sequence similarity to beta4-galactosyltransferases, but the sequence was distinct in known motifs and did not contain the cysteine residues conserved in the other six members of the beta4Gal-T family. The genomic organization of beta4Gal-T7 was different from previous beta4Gal-Ts. Expression of beta4Gal-T7 in insect cells showed that the gene product had beta1,4-galactosyltransferase activity with beta-xylosides, and the linkage formed was Galbeta1-4Xyl. Thus, beta4Gal-T7 represents galactosyltransferase I enzyme (xylosylprotein beta1, 4-galactosyltransferase; EC 2.4.1.133), which attaches the first galactose in the proteoglycan linkage region GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser. Sequence analysis of beta4Gal-T7 from a fibroblast cell line of a patient with a progeroid syndrome and signs of the Ehlers-Danlos syndrome, previously shown to exhibit reduced galactosyltransferase I activity (Quentin, E., Gladen, A., Rodén, L., and Kresse, H. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 1342-1346), revealed two inherited allelic variants, beta4Gal-T7(186D) and beta4Gal-T7(206P), each with a single missense substitution in the putative catalytic domain of the enzyme. beta4Gal-T7(186D) exhibited a 4-fold elevated K(m) for the donor substrate, whereas essentially no activity was demonstrated with beta4Gal-T7(206P). Molecular cloning of beta4Gal-T7 should facilitate general studies of its pathogenic role in progeroid syndromes and connective tissue disorders with affected proteoglycan biosynthesis.

New block copolymers based on the ionogenic block of poly(N,N-diallyl-N,N-dimethylammonium chloride) (PDADMACl) and liquid crystalline (LC) acrylate-based polymers are synthesized. The chain length of the acrylate-based block is controlled by the temperature and PDADMACl−acrylic monomer ratio. The chain length of the acrylate-based block controls the structure of the PDADMACl block whether crystalline or amorphous. Because of the “solid” state of the polyelectrolyte in domains both polymer and small ions are strongly fixed, and this provides the opportunity to reveal the polymer chain dynamics related with the LC acrylate-based polymer. The dynamics of the LC polymer in the block-copolymer is shown to be very similar to that in the homopolymer with no strong influence of polyelectrolyte blocks.

Results of dielectric studies of the low frequency relaxation process in several substances exhibiting nematic -smectic C polymorphism are presented. They are compared with the data obtained re-cently for substances with nematic-smectic A and nematic-smectic B phase sequences. It was found that the rate of molecular reorientation around the short axes does not change at the transition between the nematic and a liquid-like smectic phase (Sm A, Sm C), whereas it is considerably retarded at that of the nematic-solid-like smectic (Sm B) phase. However, the activation barrier for this motion is markedly lower in the orthogonal smectics (Sm A, Sm B) than in the nematic and Sm C phases. The analysis of numerous experimental data on the activation enthalpy in the nematic phase shows that the Arrhenius equation conforms better with results than the Diogo-Martins approach, if the nematic range exceeds 10 K.

A fourth genetic subtype of the Sanfilippo syndrome due to a deficiency of N-acetylglucosamine-6-sulfate sulfatase which is required for heparan sulfate degradation has recently been described. The clinical findings of two patients with a deficiency of this enzyme are reported here. Differential diagnosis from the other types of the Sanfilippo syndrome cannot be made by clinical criteria, but rests on specific enzyme assays. Since patients of either sex are known and consanguinity was present in one case, autosomal recessive inheritance is most probable.

Summary The mucopolysaccharidoses are a group of genetic diseases which are characterized by an excessive intralysosomal accumulation of partially degraded mucopolysaccharides. This storage is caused by the inactivity of one of eleven enzymes that are required for the degradation of the different types of mucopolysaccharides. There is a rough correlation between phenotype and chemical nature of the storage material. Similar clinical pictures, however, may be caused by an inactivity of different enzymes. Conversely, different clinical expressions of the defect of a single enzyme may be attributed to allelic mutations.

Poly(ethylene terephthalate) PETP has been modified with a difunctional alcohol and acid in the molar relation 1:1. By dielectric relaxation measurements could be shown that the modification increases the segmental mobility (a-process). The local mobility (ß-process) increases at smaller and decreases at higher concentrations of the modificators. A separation of the a-relaxation from the common relaxation process a+ß could be observed with decreasing temperature.

The phase diagram of 4-n-octyloxyphenyl 4-n-pentyloxybenzoate (nematic) and 2-methylphenylbenzoate (not liqu. cr.) was investigated. In the nematic part of the diagram the complex dielectric constants and the relaxation were evaluated as functions of the temperature and the concentration. In the isotropic state the viscosities were measured as functions of the temperature and the concentration. The results allowed the calculation of the nematic retardation factor, the nematic interaction energy E and the activation energy of the rotation of the longitudinal dipole component. E is only slightly influenced by addition of the not liquid crystalline component. The temperature and concentration dependence of the dielectric anisotropy allows the conclusion, that at a constant temperature difference from the initial clearing in the binary system there are constant values of the retardation factor and the degree of order.

AbstractBinary systems of ketones and aldehydes as proton acceptors with different donors were investigated. The existence of different hydrogen bonded liquid crystalline associates was proven by the induction of the smectic A phase as well as by IR-spectroscopic measurements.

A new class of liquid crystalline side chain polymers using swallow-tailed mesogens was synthesized. Comparative dielectric investigations on these polymers and on the corresponding low molecular weight substances in the frequency range from 10 Hz to 100 kHz should give information about the dynamic behaviour. The results obtained from the monomers agree well with those of other swallow-tailed liquid crystals and can be explained by an antiparallel orientation of the molecules in the SA phase. There are hints to a tendency to an antiparallel orientation of the side chains in the polymers, too.

Dielectric relaxation measurements in the frequency range from 1 Hz to 100 kHz on mixtures of a substituted polyacrylate and 4-n-hexyloxycyanobiphenyl have been carried out. In the mixtures the dielectric absorption properties which can be related to the individual compounds has been detected. The relaxation frequency of the low molecular compound is about 50 to 100 times higher in comparison with the δ-relaxation of the polymer but it exhibits nearly the same high activation energy. From the experimental data it can be concluded that there is a molecular disperse distribution of both compounds in which the dynamics is mainly determined by the excess component, the polymer.

Dielectric relaxation and viscosity measurements in a mixture consisting of one component with a high viscosity (A) and the basic mixture Mi 5 have been carried out. The dielectric relaxation times τA for the reorientation around the short molecular axis show a linear increase with the mole fraction of the high viscous compound xA at constant temperature. τA has been extrapolated to χA → 0 and the relaxation time of A at infinite dilution τA∞ has been estimated. The difference between the relaxation times τMi5 and τA∞ is explained by geometrical factors.

Dielectric properties of four diols having different chemical structures of the hydrophobic part were determined by the time domain spectroscopy method in the frequency range from c. 15MHz to c. 7GHz. The static permittivity clearly reflects the changes in the position of the dipole moments in the molecules. The dielectric relaxation times characterizing the diol part of the molecules are similar for all the substances studied. In the case where the phenylthiadiazole unit is built into the alkyl chain, two well separated processes were observed: one connected with the 'hydrophobic' and the second with the 'hydrophilic' part of the molecule. This emphasizes the amphotropic character of such molecules.

Cultured cells derived from bovine corneal stroma synthesize all types of sulfated glycosaminoglycans and distribute these macromolecules into topographically different compartments in a reproducible manner. Each compartment is characterized by a typical glycosaminoglycan distribution pattern. Corneal fibroblasts synthesize in vitro only small amounts of keratan sulfate in contrast to the in vivo conditions. We have, therefore, investigated the synthesis and topographical distribution of sulfated glycosaminoglycans as influenced by different culture conditions. The following results were obtained:1)Cocultivation of epithelial and stromal fibroblasts from bovine cornea led to an increased incorporation of radiosulfate into sulfated glycosaminoglycans by about 50% as compared to the theoretical value. Glycosaminoglycan distribution of mixed cultures into different compartments showed no similarity compared with pure epithelial or stromal fibroblasts.2)Addition of native or heat inactivated anterior chamber fluid to the culture medium was followed by a twofold increase of [35S]-sulfate incorporation and by an augmented intracellular and pericellular accumulation of labeled macromolecules.3)Reduction of the incubation temperature led to a reduced synthesis of glycosaminoglycans without influencing their topographical distribution. Growth of stromal cells on type I collagen was accompanied by a reduced glycosaminoglycan synthesis of about 25%. Extracellular macromolecules reached only half of the normal value, while intracellularly their concentration was slightly increased.4)None of the variations of the culture condition led to a significant change of the distribution pattern of sulfated glycosaminoglycans. Especially, no significant increase of keratan sulfate biosynthesis could be detected.

A new genetic variant of the Sanfilippo syndrome due to deficiency of acetyl CoA: a-glucosaminide N-acetyltransferase, was recently demonstrated in four patients. The clinical findings of these patients are reported here. Differential diagnosis from other types of the Sanfilippo syndrome on clinical and routine laboratory criteria is difficult and enzyme assay is necessary to reach the diagnosis. Since two of the patients reported are females and consanguinity was present in one case, autosomal recessive inheritance is most probable.

Clinical, radiological and biochemical findings of two new cases of Sanfilippo disease, type D are reported. A high percentage of heparan sulfate was found in the urinary glycosaminoglycan pattern and a severe deficiency of N-acetylglucosamine-6-sulfate sulfatase was demonstrated in skin cultured fibroblasts from the patients. One of the patients presented mild intellectual impairment which differentiates him from the other cases described to date.

Die Reaktionsdynamik, Schwerpunkt der Bunsentagung 1990, erlebt zur Zeit eine atemberaubende Renaissance: Die Laser–Spektroskopie im Pico– und Femtosekundenbereich hat's möglich gemacht. Wie aktuell immer wieder die atomaren Cluster sind, hat C60erneut bewiesen. Weitere Themen: Hochdruckthermodynamik und Flüssige Kristalle. Die Reaktionsdynamik, Schwerpunkt der Bunsentagung 1990, erlebt zur Zeit eine atemberaubende Renaissance: Die Laser–Spektroskopie im Pico– und Femtosekundenbereich hat's möglich gemacht. – Wie aktuell immer wieder die atomaren Cluster sind, hat C60erneut bewiesen. Weitere Themen: Hochdruckthermodynamik und Flüssige Kristalle.

An antiserum was raised in guinea pigs against purified normal human N-acetylgalactosamine-6-sulfate sulfatase, the enzyme affected in Morquio's disease type A. The antiserum precipitated most of N-acetylgalactosamine-6-sulfate sulfatase from a concentrate of normal human urine. The antigen-antibody complex was enzymatically active. Urine concentrates from five patients with Morquio's disease type A did not contain material competing with the normal enzyme for binding to soluble or Sepharose-bound antibodies. No precipitin arc was obtained on immunodiffusion of antiserum and urine from the single patient investigated by this method. From the sensitivity of the indirect immunoassay it was concluded that the urine of the five patients contained less than 5% of the normal amount of cross-reacting material.

Genetic heterogeneity of the Morquio syndrome has been known since deficiency of ß-galactosidase was detected in some patients in addition to the deficiency of N-acetylgalactosamine-6-sulphate sulphatase in the classical form of Morquio syndrome. The clinical findings of 11 patients with MPS IVA, the classical form, and 2 patients with MPS IV B, a variant form, are described. All of the patients with MPS IV A showed extraskeletal manifestations of their disease. The patients with MPS IV B seem to be less severely affected.

The spontaneous polarization Ps of homologous liquid crystalline thiadiazole derivatives was investigated. By elongation of the alkyloxy group attached near to the asymmetric carbon atom Ps increases from the methoxy to the hexyloxy derivative and decreases by further extension of the alkyloxy part. By chemical variation of the polarity and the molecular shape we demonstrate the importance of the steric relations for Ps.

Physicochemical and chemical properties of small proteoglycans containing galactosaminoglycan chains from cultured human skin fibroblasts and human smooth-muscle cells were compared to determine the extent of structural similarity. The proteoglycan secreted by smooth-muscle cells was of larger molecular size and of higher buoyant density, due to longer glycosaminoglycan chains, than the secretion product of skin fibroblasts. Additionally, both proteoglycans differed in the ratio of iduronic acid and glucuronic acid residues. On the other hand, degradation of secreted [3H]leucine-labelled proteoglycans with chondroitin ABC lyase followed by SDS/polyacrylamide-gel electrophoresis resulted in the appearance of core protein bands of identical size (Mr 48,000 and 45,000, depending on the number of asparagine-bound oligosaccharides). An Mr value of 40,000 was determined for the core protein of cells pretreated with tunicamycin. An antibody against the core protein from fibroblast secretions was cross-reactive with the core protein from smooth-muscle cells. Core protein accumulating intracellularly after treatment with carbonyl cyanide m-chlorophenylhydrazone exhibited, on reduction and alkylation, an isoelectric point of 7.8 in both cell types. Limited proteolysis by staphylococcal V8 serine proteinase or endoproteinase Lys-C led in both instances to the formation of peptides of identical size. Peptides bearing asparagine-bound oligosaccharides were free of glycosaminoglycan chains. Similar peptide patterns were obtained when 125I-labelled core proteins were digested with either trypsin or chymotrypsin. Thus small proteoglycans from fibroblasts and smooth-muscle cells can be differentiated by their glycosaminoglycan moieties but not by the nature of their core proteins.

Endocytosis by cultured human skin fibroblasts of 35SO4(2-)-labelled or [3H]leucine-labelled proteoglycans from fibroblast secretions and of 125I-proteodermatan sulphate from pig skin was quantitatively investigated. The following results were obtained. (1) Core proteins prepared by digestion with chondroitin ABC lyase were at least as efficiently endocytosed as native proteoglycans. Pig skin proteodermatan sulphate was a competitive inhibitor of endocytosis of 35SO4(2-)-labelled proteoglycans. (2) Proteoglycans produced in the presence of tunicamycin and native proteoglycans degraded with endoglycosaminidase H were internalized at a normal rate. Several monosaccharides that can be bound by mammalian lectins were unable to influence the internalization of proteoglycans. Treatment of proteoglycans with neuraminidase, however, resulted in an increased clearance rate. (3) Reductive methylation or acetoacetylation of lysine residues was accompanied by a parallel decrease in the rate of proteoglycan endocytosis. Reversal of acetoacetylation normalized the uptake properties. Endocytosis of native proteoglycans was also reduced in the presence of poly-L-lysine, and this reduction in endocytosis was observed as well with proteoglycans synthesized in the presence of the lysine analogue S-2-aminoethylcysteine. These results suggest that the recognition marker required for receptor-mediated endocytosis of proteodermatan sulphate resides in its protein moiety and involves lysine residues.

Upon incubation of keratan [35S]sulphate with normal fibroblasts both [35S]sulphate and N-acetylglucosamine 6-[35S]sulphate are liberated. From the products obtained after digestion with various mutant fibroblasts and with purified N-acetylgalactosamine 6-sulphate sulphatase we suggest that (i) [35S]sulphate is released almost exclusively from galactose 6-sulphate residues; (ii) N-acetylgalactosamine 6-sulphate sulphatase exhibits galactose 6-sulphate sulphatase activity; (iii) both sulphatase activities are deficient in Morquio disease type A.

Measurements of the temperature and frequency dependence of dielectric constants have been performed for five homologues in the range 100 Hz -10 MHz. These substances exhibit a negative anisotropy of the dielectric constants and two relaxation regions (rotation of the molecules around the short resp. long axis) in the investigated frequency range. Even in the crystalline state dipolar reorientations are possible which have been interpreted as rotations of the alkoxy group. Changes of the static dielectric constants, relaxation frequencies and transition entropies are discussed as a measure of structural changes passing the several liquid crystalline phases.

New ferroelectric smectic thiadiazole derivatives are presented. The dependence of the spontaneous polarization on the chemical structure of the chiral centre and of the mole fraction of achiral-chiral mixtures is discussed.

Transition temperatures, both principal relaxation times and respective activation enargies have been found for the first five members of the pentylphenyl - alkoxythiobenzoate homologous series. It has been found that the transition temperatures exhibit a weakly descanding odd-even effect whereas all dynamic quantities increases almost continuously with the number of carbon atoms in the alkoxy chain.

Results of dielectric relaxation studies of two members of 4, 4'-n-alkoxyazoxybenzene homologous series, 3.OAOB and 5.OAOB, are presented. On the basis of dielectric spectra obtained for parallel (ε∥*) and perpendicular (ε⊥*) orientations of the samples with respect to measuring electric field the following problems are discussed: (i) the sign change of dielectric anisotropy when frequency increases from radio to microwave range; (ii) influence of the local field factor on the dipole correlation time in the nematic phase, and (iii) mechanism of molecular reorientations taking into consideration the dielectric spectra of three substances having different electric structures. It was concluded that the main molecular process contributing to the high frequency dielectric spectra of the nematic phases is the reorientation around the long axis of molecule as a whole, characterized by the relaxation time τ⊥DR ≅ 85 ps, whereas the QNS method reflects the internal reorientations of two molecular moieties around N - phenyl bonds with the correlation times τQNS = (4 ÷ 9) ps.

Four cyano-substituted liquid crystals of different length to width ratio have been added to a nematic basic mixture. Their influence on the dielectric relaxation process observed parallel to the nematic director was investigated in the frequency range from 0.1 to 100 kHz. The decrease of the relaxation frequency by increasing molecular length has been correlated to the molecular geometry as well as to the increasing activation energy.

The geometrical anisotropy in the shape of swallow-tailed ST liquid crystalline molecules results in an extremely strong tendency of an antiparallel order in the short range. Dielectric measurements on a binary system of a ST and a double ST compound show that even at a mole fraction of 0.5 this effect can be observed. The strong deviations from the statistical distribution of the directions of the molecular long axis is caused by the asymmetric repulsive forces and the dipole-dipole interaction.

The chondroitin/dermatan sulfate proteoglycan decorin is known to interact via its core protein with fibrillar collagens, thereby influencing the kinetics of fibril formation and the final diameter of the fibrils. To define the binding site(s) for type I collagen along the core protein, which is mainly composed of leucine-rich repeat structures, decorin cDNAs were constructed and expressed in human kidney 293 cells. The constructs encoded (i) C-terminally truncated molecules, (ii) core proteins with deletions of selected leucine-rich repeats, or (iii) various point mutations. The deletion of the sixth leucine-rich repeat Met176-Lys201 and the mutation E180K drastically interfered with the binding to reconstituted type I collagen fibrils. In contrast, the deletion of the seventh repeat Leu202-Ser222 led at the most to a marginally impaired binding, although the secretion of this proteoglycan was abnormally low. Decorin with two other point mutations in the sixth leucine-rich repeat, Lys187 --> Gln and Lys200 --> Gln, respectively, bound type I collagen either normally or even better than the normal recombinant proteoglycan. These data suggest that a major collagen-binding site of decorin is located within the sixth leucine-rich repeat and that glutamate-180 within this repeat is of special importance for ionic interactions between the two matrix components.

Biosynthesis and secretion of proteodermatan sulfate produced by cultured human skin fibroblasts were investigated employing immunological procedures. During an incubation period of 10 min in the presence of [3H]leucine, two core protein forms of Mr = 46,000 and 44,000, respectively, were synthesized. They were converted to mature proteodermatan sulfate with a half-time of approximately 12 min. Fifty per cent of total mature proteodermatan sulfate were found in the culture medium after a 35-min chase. Six to eight per cent remained associated with the cell layer after a chase of 6 h. In the presence of tunicamycin, fibroblasts synthesized a single core protein of Mr = 38,000 that was converted to mature proteodermatan sulfate and secreted with similar kinetics as the N-glycosylated species. Subtle differences in the molecular size of core proteins were noted when cell-associated and secreted proteodermatan sulfate were degraded with chondroitin ABC lyase, but core proteins free of N-linked oligosaccharides were identical. Labeling with [3H]mannose revealed that secreted proteodermatan sulfate contains two or three complex-type or two complex-type and one high-mannose-type N-linked oligosaccharide chains. The N-glycans are bound to a 21-kDa fragment of the core protein. After incubation in the presence of [3H]glucosamine, the [3H]galactosamine/[3H]glucosamine ratio was 3.76 and 3.30 for secreted and cell-associated proteodermatan sulfate, respectively. Evidence for the presence of O-linked oligosaccharides could not be obtained. Small amounts of core protein free of dermatan sulfate chains were secreted when the cultures were treated with p-nitrophenyl-beta-D-xyloside.