Showing papers on "Chitin published in 1980"

Distribution of chitin in the yeast cell wall. An ultrastructural and chemical study.

Abstract: The distribution of chitin in Saccharomyces cervisiae primary septa and cell walls was studied with three methods: electron microscopy of colloidal gold particles coated either with wheat germ agglutinin or with one of two different chitinases, fluorescence microscopy with fluorescein isothiocyanate derivatives of the same markers, and enzymatic treatments of [14C]glucosamine-labeled cells. The septa were uniformly and heavily labeled with the gold-attached markers, an indication that chitin was evenly distributed throughout. To study the localization of chitin in lateral walls, alkali-extracted cell ghosts were used. Observations by electron and fluorescence microscopy suggest that lectin-binding material is uniformly distributed over the whole cell ghost wall. This material also appears to be chitin, on the basis of the analysis of the products obtained after treatment of 14C-labeled cell ghosts with lytic enzymes. The chitin of lateral walls can be specifically removed by treatment with beta-(1 leads to 6)-glucanase containing a slight amount of chitinase. During this incubation approximately 7% of the total radioactivity is solubilized, about the same amount liberated when lateral walls of cell ghosts are completely digested with snail glucanase yield primary septa. It is concluded that the remaining chitin, i.e., greater than 90% of the total, is in the septa. The facilitation of chitin removal from the cell wall by beta-(1 leads to 6)-glucanase indicates a strong association between chitin and beta-(1 leads to 6)-glucan. Covalent linkages between the two polysaccharides were not detected but cannot be excluded.

Interaction of lead and chromium with chitin and chitosan

Abstract: The interaction of the natural marine polymer chitin and its deacetylated derivative chitosan with lead and chromium has been investigated. The uptake of lead and chromium was determined from changes in concentration as measured by atomic absorption spectroscopy. A significant uptake of Pb(II) on both chitosan and chitin was observed. However, the uptake of Pb(II) on chitin was approximately 21% of that on chitosan. The number of Natoms in chitin and chitosan and per number of Pb(II) ions sorbed was 115 and 29, respectively. The number density of flakes observed in the scanning electron microscope and characterized by an intense Pb signal in energy dispersive analysis of x rays (EDAX) was greater on the surface of chitosan [containing 1.7 × 10−4 mole Pb(II)/g chitosan] than chitin [containing 3.5 × 10−5 mole Pb(II)/g chitin] after equilibration with Pb(II) solution. The bonding state of lead on chitosan as determined by electron spectroscopy for chemical analysis (ESCA) is similar to the bonding of lead in PbO based on the Pb 4f7/2 binding energy. A significant shift in the O 1s binding energy from 532.2 to 531.4 eV was observed for chitosen after equilibration with Pb(II) solution. The caculated values of the N/Pb ratio from ESCA spectra were 0.5 and 11, for chitosan and chitin, respectively. A significant uptake of Cr(III) on chitosan was observed and a significant increase in the pH of solutions of Cr(III) on equilibration with chitosan occurred. A high number density of nodules characterized by an intense Cr signal in EDAX was observed in chitosan [containing 2.5 mole Cr(III)/g chitosan] after equilibration with Cr(III) solution. The calculated values of the N/Cr ratio from ESCA spectra was 18 for chitosan.

Influence of manganese on morphology and cell wall composition of Aspergillus niger during citric acid fermentation.

Abstract: Morphology and cell wall composition of Aspergillus niger were studied under conditions of manganese sufficient or deficient cultivation in an otherwise citric acid producing medium. Omission of Mn2+ (less than 10-7 M) from the nutrient medium of Aspergillus niger results in abnormal morphological development which is characterized by increased spore swelling, and squat, bulbeous hyphae. Fractionation and analysis of manganese deficient cell walls revealed increased chitin and reduced β-glucan contents as well as reduction of galactose containing polymers, as compared to cell walls from manganese sufficient grown hyphae. Addition of copper induced the same effect as manganese deficiency, both on morphology and cell wall composition. Addition of cycloheximide also produced a very similar type of morphology with increased chitin and reduced β-glucan contents of the cell wall but its effect on galactose was less pronounced.

Regulation of chitin synthesis during germ-tube formation in Candida albicans

Abstract: The synthesis of chitin during germ-tube formation in Candida albicans may be regulated by the first and last steps in the chitin pathway: namely l-glutamine-d-fructose-6-phosphate aminotransferase and chitin synthase. Induction of germ-tube formation with either glucose and glutamine or serum was accompanied by a 4-fold increase in the specific activity of the aminotransferase. Chitin synthase in C. albicans is synthesized as a proenzyme. N-acetyl glucosamine increased the enzymic activity of the activated enzyme 3-fold and the enzyme exhibited positive co-operativity with the substrate, UDP-N-acetylglucosamine. Although chitin synthase was inhibited by polyoxin D (Ki =1.2μM) this antibiotic did not affect germination. During germ-tube formation the total chitin synthase activity increased 1.4-fold and the expressed activity (in vivo activated proenzyme) increased 5-fold. These results could account for the reported 5-fold increase in chitin content observed during the yeast to mycelial transformation.

Dynamic mechanical behavior of chitin and chitosan

Abstract: Recently, much attention in the many fields has been paid to chitin(Poly-N-acetyl-D-glucosamine), which is formally considered an aminocellulose derivative that occurs widely in nature, for example, in the hard shell of insect and crustaceans, cuttlefish bone, and the cell walls of fungi, and its derivative, chitosan (Poly-D-glucosamine), which is readily obtained from chitin by N-deacetylation with alkali. However, there has been few papers concerning the physical properties of these polysaccharides. FUKADA et ai.(1975) examined the piezoelectricity of highly crystalline s-chitin, and found that a temperature dispersion appears only around -95~ which has been assigned to the water strongly bound to s-chitin. More recently, BRADLEY et ai.(1976) studied dynamic mechanical properties of some polysaccharides such as cellulose, amylose, and dextran containing various amount of water, and have characterized four mechanical transitions. In this paper, we report the effect of water on the dynamic mechanical properties of chitin and chitosan as a function of temperature.

Utilization of Imaginal Tissues from Pupae of the Stable Fly for the Study of Chitin Synthesis and Screening of Chitin Synthesis Inhihitors

Abstract: Imaginal epidermal tissues from 4-day-old pupae of Stomoxys calcitrans (L.) were used to develop an assay suitable for studying chitin synthesis and for screening chitin synthesis inhibitors. Four chitin precursors, D -glucose, D -glucosamine, D -fructose, and N -acetyl- D -glucosamine were found to be suitable substrates in this assay system. All these substrates were incorporated into chitin. Maximum incorporation occurred within 8 h or less. The apparent I50’s of diflubenzuron (Dimilin; TH-6040; N -[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide), Bay Sir 8514 (2-chloro- N -[[[4(trifluoromethoxy) phenyl] amino] carbonyl] benzamide), EL-494 (N-[[[5-(4-bromophenyl)-6-methyl-2-pyrazinyl]-amino]carbonyl]-2,6-dichlorobenzamide), and polyoxin D for inhibition of NAGA incorporation were found to be 52, 440, 8,600 and 13,000 nM, respectively.

Chitin containing poly-ion complex

Abstract: This invention relates to a poly-ion complex comprising chitin or N-acylchitosan derivative having carboxymethyl and polyelectrolyte.

Studies on Chitin. IV. Preparation of Acetylchitin Fibers

Abstract: Solutions of variously acetylated chitin in formic acid were prepared by freezing with addition of dicholoroacetic acid or organic solvent, and spun into diisopropyl ether to give acetylchitin fibers 10 Acetylchitin fiber was also obtained by the direct acetylation of chitin fiber in a perchloric acid–acetic anhydride mixture 11 Acetylated chitin fiber showed the maximum tenacity, elongation, and knot strength among the variously acetylated chitin fibers, while a maximum Young’s modulus was shown by the 16 acetylchitin fiber Acetylchitin fibers have the advantage of greater tenacity and elongation in comparison with chitin fiber These advantages contribute to the practical usefulness of chitin in spite of its poor solubility in most solvents and poor reactivity toward chemical reagents Also the acetylchitin film prepared from formic acid–dichloroacetic acid mixture is softer and thus more pleasing to the touch than chitin film

Structure and composition of pithophora oedogonia (chlorophyta) cell walls1

Abstract: Carbohydrates, amino acids and other cell wall components of Pithophora oedogonia (Montagne) Wittrock were identified by physical, biochemical, and cytochemical techniques as well as by light and electron microscopy. The major polysaccharides of P. oedogonia cell walls were cellulose and chitin. In addition to N-acetylglucosamine and glucose, N-acetylgalactosamine, galactose, arabinose, fucose, mannose, xylose, and galacturonic acid were the other sugars, amino sugars, and sugar derivatives detected. The carbohydrate content of the cell walls was estimated to be 65% non-nitrogenous hexose and 6% chitin. Chitin was present in the crosswall disks and outer wall, whereas cellulose was confined to the inner wall. Protein and N- acetylgalactosamine were concentrated in the chitin-rich wall fraction. The location of chitin in P. oedogonia cell walk is suggested as a basis for morphological differences between the two genera, Cladophora and Pithophora.

Kinetics of β-glucan and chitin formation by cells and protoplasts of the yeastSaccharomyces cerevisiae

Abstract: Intact cells and protoplasts of the yeastSaccharomyces cerevisiae were grown in liquid medium with radioactive glucose as the sole carbon source, and the kinetics of radioactivity incorporation into β-glucan and chitin fractions were measured and compared. While the synthesis of β-glucan by protoplasts started early after their being suspended in the growth medium, the onset of chitin formation was delayed about 3 h and, unlike β-glucan, its formation depended on synthesis of undisturbed protein. In the intact cells, the ratio of β-glucan to chitin was constantly around 12 during growth; while in protoplasts this ratio steadily decreased in the course of cultivation and reached the value of 1.1 after 16h, which can be ascribed to the higher rate of chitin formation by protoplasts in comparison with normal cells. The deproteinized polysaccharide nets formed on the surface of protoplasts that had been incubated in the presence and in the absence of cycloheximide did not differ substantially in their morphology. The only observed difference was the presence of granular material in the samples from control protoplasts grown in the absence of cycloheximide.

Inhibition of chitin biosynthesis in cultured imaginal discs: Effects of alpha-amanitin, actinomycin-D, cycloheximide, and puromycin

Abstract: Wing imaginal discs isolated from last instar larvae of the Indian meal moth,Plodia interpunctella, produced chitin when incubated in vitro with ≧2×10−7 M 20-hydroxyecdysone. Chitin biosynthesis was initiated 8 h after the conclusion of a 24-h treatment with hormone. Simulataneous incubation of wing discs with 20-hydroxyecdysone and either inhibitors of RNA synthesis (alpha-amanitin, actinomycin-D) or inhibitors of protein systhesis (cycloheximide, puromycin) prevented chitin biosynthesis. We conclude from our results that RNA and protein synthesis must continue undiminished during the hormone-contact period, and that synthesis of protein, but not of new RNA is required during the posthormone culture period. Our findings are consistent with the hypothesis that ecdysteroids stimulate insect metamorphosis by promoting the synthesis of new RNA and protein during a hormone-dependent phase followed by hormone-independent protein synthesis.

Preparation of waterrsoluble alkali chitin

Abstract: PURPOSE:To obtain an alkali chitin completely soluble in ice water, by at least one procedure for the penetration of an alkali into a chitin powder, by means of freezing and application of pressure, after homogeneous absorption of an aqueous alkali solution into the chitin powder at a low temperature. CONSTITUTION:Water, in which a chitin powder is dispersed, is boiled at 0.1- 5kg/cm , at 103-160 deg.C, and then filterpressed. The obtained water-containing chitin powder is dispersed into a 20-60wt%, preferably about 40wt%, aqueous solution of NaOH or KOH. By applying pressure on the resulting aqueous solution of alkali chitin, it is impregnated with the alkali solution. Then the obtained alkali chitin is frozen at <=-10 deg.C, preferably <=-20 deg.C, by which the water within the micelle is crystallized and expanded, causing penetration of the alkali solution. Then it is thawed, and the solution is allowed to further penetrate by means of freezing at <=15 deg.C and application of pressure. Although it is possible to effect the penetration by means of one procedure, it is preferable to accomplish it by repeating the procedure, in oder to obtain effective results.

Material produced from cross-linked ionic chitin derivative, its preparation and use

Abstract: Problems have occurred using chitin derivatives having surface ionic groups as ion-exchangers. These problems can be overcome by employing a material produced by acylating or treating with an acid the surface of a material composed of a cross-lined ionic chitin derivative. The acylation or acid treatment eliminates the surface ionic groups, for example by converting them to non-ionic groups. The resulting material can also be employed in dialysis and in the separation and purification of glycoproteins.

Process for preparing porous shaped material of acylated chitin derivative

Abstract: A process for producing a porous shaped material of acylated chitin derivative wherein a soluble derivative of chitin is acylated, characterized in that an aqueous solution of the derivative of chitin containing a diluent, a porosity-regulating agent and a surfactant is added into a solution of an organic acid anhydride containing a surfactant.

Cell walls of filamentous fungi

Abstract: Fungal walls, like those of plants and bacteria, consist of a rigid layer outside the protoplast, which they protect from osmotic and other changes in the environment. In addition they are responsible for the characteristic shape of the cell and have to be modified when the cell changes, as for instance during the growth of a hyphal tip, the initiation of a branching hypha, the change to a conidiospore, or from mycelial to yeast-like growth or vice versa. The wall is composed largely of polysaccharides, with some protein and lipid, although the latter represents only a small proportion. It has been known for a long time that one of the chief polysaccharides is chitin, the homopolymer of β-1, 4-N-acetylglucosamine that also occurs in the integument of arthropods, and another β-1, 4-glucose, ie cellulose. Where present, both chitin and cellulose have been identified by X-ray powder crystallography and shown to be the same as authentic samples from other sources [3, 37]. These two polymers form the fibrils that make the rigid component of most fungal walls, in contrast to the yeasts where other glucose polymers, along with a small amount of chitin, take over this function [4, 7]. Before looking in detail at the other polysaccharides present, we will examine the evidence for the minor components, protein and lipid, as integral parts of the wall. Walls that have been isolated and washed as thoroughly as possible [43] still contain about 5–10% of lipid, but so far this has not been well characterized [40]. It is noteworthy, however, that mycelial walls of Penicillium charlesii contained as much as 37.5% lipid [15] and the wall of a strain of Aspergillus nidulans has been reported to have half its 10% of galactose in the form of a glycolipid [47]. The residual protein, on the other hand, can sometimes be extracted by detergents as in Aspergillus nidulans [14], whereas in other instances such as Aspergillus niger and Chaetomium globosum it resists even protracted extraction with 8 M urea [33]. Analysis of the latter firmly-attached protein and its peptic digests suggested that many acidic peptide sequences were present and showed high serine and threonine contents, as often observed in the protein of yeast walls. The importance of protein in the wall was emphasized by Hunsley and Burnett [24], who used a succession of glycanases and the proteolytic enzyme pronase to ‘dissect’ fungal walls. They concluded that in the wall of Neurospora crassa, for instance, there was a glycoprotein reticulum embedded in easily-removable protein, beneath which lay a separate protein layer, which was in turn outside and possibly intermingled with the innermost layer of chitin microfibrils. It is now clear that, in some although not all fungi [46], as hyphae extend two separate kinds of wall are laid down, a primary wall consisting of chitin microfibrils covered with protein which is laid down as tip extension proceeds, and a layer of secondary wall that is later deposited on the outside. All layers may thicken as maturation occurs, except that the inner chitin layer of N. crassa appears not to change [45] (Fig. 13.1). Another process that intervenes, but is at present little understood, is rigidification, whereby the primary wall that is first deposited in a relatively plastic state becomes more rigid as it thickens and adopts the shape and diameter of the final hyphal tube. It has been suggested that rigidification may correspond either to a diminution in the activity of autolysins or to an increasing resistance to these enzymes as the wall matures [45], though no mechanism for either process is known at present.

Production of formed product of chitosan

Abstract: PURPOSE: Chitosan resulting from hydrolysis of chitin that is widely distributed in crustaceans or its salt is dissolved in water and the solution is dry-wet formed using an aqueous solution containing a basic substance to produce a novel type of formed products such as fiber. CONSTITUTION: Chitin that is widely distributed in outer shells of crustaceans such as lobster or crab is hydrolyzed with a conc. alkali to form chitosan composed of 2-amino-2-deoxy-D-glucose. Then, the product in flakes is previously suspended in water and mixed throughly. Then, an aqueous acetic acid is added to dissolve it into a dope. The dope is extruded, e.g., through a spinning nozzle into a coagulation bath of an aqueous solution of a basic substance such as sodium hydroxide according to a wet or dry method to give the objective formed product. COPYRIGHT: (C)1981,JPO&Japio