Mechanisms of bioadhesion of macrophytic algae

During the evolution the benthic macrophytic algae developed effective mechanisms of bioadhesion enabling their attachment to almost any surface in the aqueous medium. The attachment of algal spores and zygotes includes two successive stages: the primary and the secondary (final) adhesion. Analysis of information on the composition of adhesive materials and attachment mechanisms in brown, green, and red marine macrophytes indicates that synthesis and release of adhesive substances by algal cells can be considered as a temporary intensification of cell wall synthesis. The structure of the primary adhesive material comprises a gel phase (alginate, ulvan, and agar gels) and a structuring component, i.e., a flexible network based on branched chains and/or rings of phenolic compounds, polysaccharides, or glycoproteins. Irreversible hardening of the primary adhesive material arises from phenol polymerization catalyzed by different peroxidases (brown algae) or from polymerization of glycoproteins comprising amino acids with phenolic residues (red algae). In parallel with these processes, covalent cross-links are being formed between the adhesive structural components and the gel phase polysaccharides. This results in the formation of the secondary adhesive and in eventual attachment of the organism to the substrate. The attachment mechanisms of benthic algae appear to have some features in common with the mechanisms of bioadhesion of marine invertebrates.     

Interaction of sialoglycoproteins with wheat germ agglutinin-sepharose of varying ratio of lectin to Sepharose. Use for the purification of mucin glycoproteins from membrane extracts

The influence of varying the amount of wheat germ agglutinin immobilized on Sepharose beads on the binding of glycoproteins to these beads was investigated. A series of wheat germ agglutinin-Sepharose gels containing between 0.10 and 10.0 mg of lectin/ml of gel was prepared, and the actual lectin content was established by acid hydrolysis of the gel followed by analysis of glycine, a major amino acid in wheat germ agglutinin. Affinity chromatography of labeled glycoproteins indicated that glycophorin bound to all the wheat germ agglutinin-Sepharose preparations. Fetuin, ovomucoid, and alpha 1-acid glycoprotein bound not at all or very poorly to gels with a low content of wheat germ agglutinin (less than 0.95 mg/ml). The specific binding of these glycoproteins increased with increasing lectin content on the gels, and on gels of high content (greater than 3 mg/ml) the binding was virtually quantitative. On chromatographing a mixture of glycophorin, alpha 1-acid glycoprotein, fetuin, and ovomucoid on wheat germ agglutinin-Sepharose, containing 0.08 mg of lectin/ml of gel, glycophorin was selectively retained on the gel. It was possible to purify glycophorin from an extract of human erythrocyte membranes in one step by chromatography on the above gel. By using the series of gels, it was demonstrated that Morris hepatoma 7777 membranes contained at least 4-fold more sialoglycoproteins which bound to low density wheat germ agglutinin-Sepharose compared to rat liver membranes. These hepatoma sialoglycoproteins were isolated, purified, and partially characterized as having a high proportion of O-linked sialyloligosaccharides. Our studies illustrate the use of low density wheat germ agglutinin-Sepharose gels both for the detection and for easy isolation of mucin-type glycoproteins from crude extracts of cells or membranes.     

Rheological properties and mechanical stability of new gel-entrapment systems applied in bioreactors

The mechanical stability of gels applied for entrapment and retention of biocatalysts in bioreactors is of crucial importance for successful scale-up applications. Gel abrasion in agitated reactors will depend on liquid shear, bubble shear, and wall shear, as well as collisions between the gel particles. As a simplified standardized model system, abrasion of gel beads was studied in 1-m-high bubble columns with controlled aeration, and quantified by measuring the loss of gel material into solution. Gel beads were also taken out to measure stress-strain response during controlled compression. More general rheological properties of different gels were studied by applying a variety of regimes of controlled compression of standardized gel cylinders: Gel strength was measured by recording the fracture properties and the Young's modulus. Viscoelastic properties were revealed by recording creep during compression as well as recovery after compression. Oscillation tests up to 1000 cyclic compressions were applied to compare the fatigue of different gels. Results obtained for Ca-alginate gels, gels of chemically modified polyvinyl alcohol with stilbazolium groups (PVA-SbQ) as well as mixed gels of Ca-alginate and PVA-SbQ are compared with previously published data for kappa-carrageenan, agar, and polyethylene glycol (PEG) gels. It is concluded that material fatigue rather than mechanical properties such as stiffness or fracture stress should be considered when selecting a suitable gel material on the basis of abrasion resistance. The very soft and superelastic PVA-SbQ gel showed no significant fatigue in mechanical tests and no abrasion was detected in the standardized model system used. Ca-alginate gels, however, showed severe irreversible changes due to fatigue at oscillating loads and creep at constant load. Due to their similarities with kappa-carrageenan gels in mechanical tests, it is likely that Ca-alginate would also be sensitive to abrasion. Mixed gels of Ca-alginate and PVA-SbQ represent a complex system with intermediate properties, showing significant fatigue and creep, but elastic properties from the PVA-SbQ gel make it less sensitive than the pure Ca-alginate gel.     

Estimating glycoprotein carbohydrate chain structures by lectin reactivities in polyacrylamide gels

Complex mixtures of cellular glycoproteins contain a myriad of different carbohydrate chains that cannot be easily analyzed without rigorous purification of each individual glycoprotein. We have analyzed the carbohydrate chains in complex mixtures of cellular glycoproteins by separation using sodium dodecyl-sulfate polyacrylamide gel electrophoresis and interacting the gels with several 125I-labeled lectins. By use of in situ chemical modifications of the glycoproteins after their electrophoretic separation together with the known carbohydrate-binding specifities of several lectins, it has been possible to estimate glycoprotein carbohydrate chain structures. As an example we have examined the cellular glycoproteins of a ovary-colonizing metastatic variant of B16 melanoma and report the types of carbohydrate chains that are found on various melanoma glycoproteins.     

Rotational diffusion of short DNA fragments in polyacrylamide gels: an electric birefringence study

Using electric birefringence we have examined the rotational diffusion of five short DNA fragments (55 to 256 base pairs) both in polyacrylamide gels as a function of gel concentration and in solution. The length dependence of the measured rotational relaxation times in the gels is in good agreement with the prediction from the Odijk theory for the dynamics of slightly flexible rods in a network. The rotational relaxation times were found to depend on the gel concentration, contrary to the prediction from the Odijk theory. Possible reasons for this observation are discussed. The birefringence decay curves for DNA fragments in the gel were single exponential only at small electric field strength.     

An improved formulation of SYPRO Ruby protein gel stain: comparison with the original formulation and with a ruthenium II tris (bathophenanthroline disulfonate) formulation

SYPRO Ruby protein gel stain is compatible with a variety of imaging platforms since it absorbs maximally in the ultraviolet (280 nm) and visible (470 nm) regions of the spectrum. Dye localization is achieved by noncovalent, electrostatic and hydrophobic binding to proteins, with signal being detected at 610 nm. Since proteins are not covalently modified by the dye, compatibility with downstream proteomics techniques such as matrix-assisted laser desorption/ionisation-time of flight mass spectrometry is assured. The principal limitation of the original formulation of SYPRO Ruby protein gel stain, is that it was only compatible with a limited number of gel fixation procedures. Too aggressive a fixation protocol led to diminished signal intensity and poor detection sensitivity. This is particularly apparent when post-staining gels subjected to labeling with other fluorophores such as Schiff's base staining of glycoproteins with fluorescent hydrazides. Consequently, we have developed an improved formulation of SYPRO Ruby protein gel stain that is fully compatible with commonly implemented protein fixation procedures and is suitable for post-staining gels after detection of glycoproteins using the green fluorescent Pro-Q Emerald 300 glycoprotein stain or detection of beta-glucuronidase using the green fluorescent ELF 97 beta-D-glucuronide. The new stain formulation is brighter, making it easier to manually excise spots for peptide mass profiling. An additional benefit of the improved formulation is that it permits staining of proteins in isoelectric focusing gels, without the requirement for caustic acids.     

水稻可溶性糖蛋白的纯化与鉴定研究

从水稻鲜叶中提取总蛋白,对总蛋白中的蛋白质含量进行了测定;通过硫酸铵沉淀将总蛋白提取液进行分级,从而达到了总蛋白细分和放量的目的。四级份的分级蛋白分别通过ConA-Sepharose 4B 亲和层析进行糖蛋白纯化,按吸收峰收集的各级糖蛋白混合物进行冷冻干燥,得到干粉;结合PAS法染色和考马斯亮蓝R-250染色对四级份的糖蛋白样品鉴定,在其中3个级份中均检测出糖蛋白;由于感度的差异,按考马斯亮蓝R-250染色可检测出近30种糖蛋白(包括部分糖肽),按PAS法染色可检测到7种糖蛋白;对3种含量较高的糖蛋白进行了胶上纯化,3种糖蛋白的PAS法染色均证实了3种样品为单一的糖蛋白或者糖肽,分别命名为RG1、RG2和RG3。     

The glycoproteins of Dictyostelium discoideum. Changes during development.

The glycoproteins of D. discoideum have been analyzed by direct binding of radio-iodinated lectins to SDS gels of the successive developmental stages. Compared with the total pattern of proteins, many changes are found in the glycoproteins during development. WGA reacts with few gel bands from the vegetative cells and most of these, including a very intense band at the top of the gel, are lost during the first few hours of development. Approximately half-way through the developmental cycle at least 14 new glycoproteins reacting with WGA begin to appear and progressively accumulate. In contrast, ConA labels many glycoproteins over the complete molecular weight range and most are unaffected during development. Lectins which bind fucose label a single component at the top of the gel of vegetative cells and this decreases rapidly as development begins. No other reactive gel bands are revealed by fucose-binding lectins until the final stages of spore and stalk formation, when four high molecular weight glycoproteins are detected. Lectins specific for terminal galactose residues and for N-acetyl-galactosamine, including the intrinsic lectins produced by D. discoideum during its development, failed to reveal any reactive glycoproteins.     

Electrophoretic analysis of four high molecular weight sialoglycoproteins produced by metastatic human colon carcinoma cells

We have found that polyacrylamide gel electrophoresis in 3% gels in the presence of sodium dodecyl sulfate is suitable for the separation of cellular glycoproteins having molecular weights ranging from 200,000 to 1,000,000. The gels secured on a rigid support (Gelbond) allow blotting techniques with lectins and antibodies for the detection of glycoproteins. Using these methods we have separated lysates of HT-29 human colon carcinoma cells and detected at least four distinct high molecular weight sialoglycoproteins having molecular weights of 900,000, 740,000, 560,000, and 450,000. The expression of the 900,000 component, as revealed by wheat germ agglutinin binding, was much higher in a subline of HT-29 cells established from liver metastases in a nude mouse than it was in the parental cells. The relative intensity of wheat germ agglutinin binding to these four sialoglycoprotein components differs depending upon their growth phase in vitro. These glycoproteins were also detectable by the binding of peanut agglutinin, provided the glycoproteins were previously treated in the gels with mild acid to remove the sialic acid from their carbohydrate chains, suggesting that mucin-type carbohydrate chains are present on these glycoproteins. The same set of glycoproteins can be detected by metabolic labeling of the cells with [3H]glucosamine in tissue culture. Very similar glycoprotein profiles are revealed by metabolic labeling of fresh colon carcinoma tissues with [3H]glucosamine in vitro.     

Proteins Specified by Herpes Simplex Virus: II. Viral Glycoproteins Associated with Cellular Membranes

Membranes prepared from HEp-2 cells infected with herpes simplex virus and free from soluble proteins, virus, ribosomes, and other cellular constituents were solubilized and subjected to electrophoresis on acrylamide gels. The electropherograms showed the following. (i) The synthesis of host proteins and glycoproteins ceases after infection. However, the spectrum of host proteins in membranes remains unaltered. (ii) Between 4 and 22 hr postinfection, at least four glycoproteins are synthesized and bound to the smooth cytoplasmic membranes. On electrophoresis, these glycoproteins form two major and two minor bands in the gel and migrate with proteins ranging from 50,000 to 100,000 daltons in molecular weight. (iii) The same glycoproteins are present in all membranes fractionated by density and in partially purified virus. The implications of the data are discussed.     

An improved mechanically durable electrophoresis gel matrix that is fully compatible with fluorescence-based protein detection technologies

Unfortunately, conventional large-format polyacrylamide gels are mechanically fragile, often tearing during the subsequent manipulations required for visualization of the proteins. This problem is compounded when large-format two-dimensional gels are subjected to multiple staining procedures in order to detect different classes of proteins, such as total protein, phosphoproteins, and glycoproteins. A mechanically durable liquid polyacrylamide-based matrix has been developed that, upon polymerization, facilitates the handling of one-dimensional and two-dimensional gels. The matrix, referred to as Rhinohide liquid acrylamide, is stable as a refrigerated solution for up to one year, and forms a polymer-reinforced polyacrylamide gel suitable for electrophoresis, upon addition of catalysts. The matrix is superior to previously reported durable gel matrices in that it does not cause distortion of high-molecular-weight bands and does not suffer from other spot morphology artifacts, such as doubling of protein spots in the molecular weight dimension. The matrix is particularly valuable for the analysis of proteins applying multiple applications of fluorescent dyes, as required with serial staining of proteins for phosphorylation, glycosylation, and total protein expression, using Pro-Q Diamond phosphoprotein stain, Pro-Q Emerald glycoprotein stain and SYPRO Ruby protein gel stain, respectively.     

Specific glycoprotein changes during development of the chick neural retina

After separation of whole proteins of chick neural retina by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), a number of glycoproteins can be detected by staining the gels with 125I-labeled wheat germ agglutinin (WGA) and other lectins. The glycoprotein patterns show both quantitative and qualitative changes between days 7 and 13 of development. Some of these glycoproteins can be separated by chromatography on columns of insolubilized lectins. These observations suggest that purification of some of these glycoproteins identified by staining with radioactive lectins would yield retinal antigens which may be specific for developmental stage and cell type.     

Fibrin-fiber architecture influences cell spreading and differentiation

ABSTRACT

The mechanical and structural properties of the extracellular matrix (ECM) play an important role in regulating cell fate. The natural ECM has a complex fibrillar structure and shows nonlinear mechanical properties, which are both difficult to mimic synthetically. Therefore, systematically testing the influence of ECM properties on cellular behavior is very challenging. In this work we show two different approaches to tune the fibrillar structure and mechanical properties of fibrin hydrogels. Addition of extra thrombin before gelation increases the protein density within the fibrin fibers without significantly altering the mechanical properties of the resulting hydrogel. On the other hand, by forming a composite hydrogel with a synthetic biomimetic polyisocyanide network the protein density within the fibrin fibers decreases, and the mechanics of the composite material can be tuned by the PIC/fibrin mass ratio. The effect of the changes in gel structure and mechanics on cellular behavior are investigated, by studying human mesenchymal stem cell (hMSC) spreading and differentiation on these gels. We find that the trends observed in cell spreading and differentiation cannot be explained by the bulk mechanics of the gels, but correlate to the density of the fibrin fibers the gels are composed of. These findings strongly suggest that the microscopic properties of individual fibers in fibrous networks play an essential role in determining cell behavior.     

Influence of the sol–gel chemistry on the activity of a lipase encapsulated in a silica aerogel

Silica aerogels have been shown to be efficient encapsulation media for the lipase of Burkholderia cepacia. The present study has focused on the encapsulation of this lipase in an aerogel made from 80% tetramethoxysilane (TMOS) and 20% methyltrimethoxylsilane (MTMS), dried by the supercritical CO₂ method. By varying different parameters in the synthesis chemistry of such materials, the structure and texture of the resulting gels can be significantly affected. The aim of the present study was to examine the possible existence of correlations between modifications of the gel’s synthesis procedure, and the catalytic activity of the gel-encapsulated lipase in the esterification reaction of lauric acid with 1-octanol. The synthesis parameters studied included aging of the wet gels in different solvents, variation of the solvent used during gel synthesis, variation in the molar ratio of hydrolysis water to silicon precursor and replacement of MTMS by another alkoxide. The biocatalytic activity was found to depend significantly on these different treatments. The results were analyzed in the light of the gel texture and structure characterization, respectively analyzed by nitrogen adsorption isotherms and ²⁹Si, ¹H and ¹³C NMR. These results suggest that the main role of the aerogel is to maintain the enzyme dispersed as it would be in an aqueous solution, even though it is used in an organic solvent where the lyophilized enzyme is insoluble. The nature of the gel surface groups, in particular their capability to modify the substrates concentration inside the gel, close to the active site of the enzyme, by comparison with the concentration in the solvent outside the gel, seem to have a more secondary effect.     

Peptide inhibitors of fibronectin, laminin, and other adhesion molecules: unique and shared features

Synthetic peptides can specifically inhibit the function of certain adhesive glycoproteins in vitro and in vivo. We have compared the relative activities of a set of six variant synthetic peptides based on the sequence of fibronectin in terms of their ability to inhibit the interactions of fibroblasts with fibronectin, spreading factor/vitronectin, laminin, and native collagen gels. BHK (baby hamster kidney) and chick embryo fibroblasts spreading on these adhesive molecules displayed distinctive patterns of sensitivity to inhibition by this panel of peptides, which depended on the adhesive molecule rather than the cell type. For fibronectin, Gly-Arg-Gly-Asp-Ser was considerably more active than Arg-Gly-Asp-Ser, whereas these two peptides displayed little difference in activity in inhibiting cell adhesion to spreading factor. For both proteins, the inverted peptide sequence Ser-Asp-Gly-Arg was also moderately active, whereas closely related peptides containing a transposition, a deletion, or a single, conserved amino acid substitution were much less active. For inhibiting interactions with laminin or native type I collagen gels, Gly-Arg-Gly-Asp-Ser was only weakly active, but the inverted peptide Ser-Asp-Gly-Arg unexpectedly continued to display inhibitory activity for both attachment proteins in both cell types. Our results indicate that different adhesive processes depend on distinct peptide recognition events by a cell. However, there may be a possible common denominator among attachment proteins in a moderate sensitivity to Ser-Asp-Gly-Arg. Our study also underscores the importance of examining a full set of peptide analogs when these novel inhibitors are used to characterize biological processes.     

Steady-state and pulsed NMR studies of gelation in aqueous agarose

Steady-state and pulsed NMR techniques have been used to investigate molecular motion in sols and gels of agarose. In passing through the sol–gel transition, the molecular mobility of water molecules is reduced only by a small amount, whereas motion of the polymer chains is greatly attenuated. The results are discused in terms of the network theory of gelation, with references to the role of water in the process and the nature of the “junction zones” between polymer chains. T₂ and line-width measurements are dominated by exchange broadening. The effects of exchange rate and differences in relaxation time between the exchanging sites are discussed. The temperature hysteresis behavior of agarose gels has been investigated and the effects of “ageing” correlated with changes in nuclear relaxation times. The synergistic increase in gel strength obtained on adding locust bean gum (LBG) to agarose has been investigated. The results indicate that LBG does not form double-helix junctions and may decrease rates of gelation by steric effects. At high agarose concentration, the LBG remains mainly in solution in interstitial water, but at low agarose concentration, it is suggested that the LBG can link gel aggregates together into a self-supporting structure, producing a synergistic increase in gel strength. Comparisons have been made between the nature of the agarose–LBG interaction and agarose–cellulose interactions in biological systems.     

A laser light scattering study of gellan gels

A study of gellan has been made using the technique of photon correlation spectroscopy. It has been confirmed that gellan gels are largely stationary at a molecular level like other polysaccharide gels and quite unlike the gels of flexible polymers such as polyacrylamide. Solution-gel transitions of deacetylated gellan in 0.025MNaCl have been studied both as a function of concentration and temperature, and the results compared with those of a parallel investigation of agarose. The interstitial spaces within gellan gels have also been studied by measuring the diffusion coefficients of dextran fractions within the gels. Since all gels are nonergodic systems, the theory of dynamic light scattering from such systems is discussed insofar as it affects the present work. It has been shown that the gellan and agarose aqueous systems are fundamentally different, in that agarose does not from a solution at very low concentrations, but splits up into macroscopic gel particles. At very low concentrations, gellan forms a solution in the presence of both gelleing and nongelling ions, the molecules of which shows little change in hydrodynamic diameter with temperature in the range 20–80°C. At higher concentrations where gels are formed, both gellan and agarose exhibit hystersis in their tempertature transitions from gel to solution and solution to gel, the solution being of large molecular aggregates. The transitions are sharp, but in both cases ther is a continous rearrangement in the structural morphology over the entire temperature range on heating, rendering the system more homogeneous prior to dissociation. In the case of gellan, however, there are two distincit phases in these structural changes—this is not true of agarose. The mean mass per unit length of the gellan fibre in the presence of 0.025M NaCl is 19 k daltons/nm at 0.7% concentration and varies with concentration to the power 0.15. The mass per unit length of the agarose fibre is much larger (ca. 110 k Daltons/nm), this difference being consistent with the difference in properties at very low concentrations. © 1994 John Wiley & Sons, Inc.     

Effect of hydrophobic modification on rheological and swelling features during chemical gelation of aqueous polysaccharides

Rheological characteristics during chemical gelation with the cross-linker ethylene glycol diglycidyl ether (EGDE) of semidilute aqueous solutions of hydroxyethylcellulose (HEC) and of two hydrophobically modified analogues (HM-1-HEC and HM-2-HEC) are reported. In addition, rheological features of gelling samples (dextran and its hydrophobically modified analogue (HM-dextran)) of a different structure have been examined. Some swelling experiments on these gels in the postgel region are also reported. The gelation time of the hydroxyethylcellulose systems decreased with increasing cross-linker concentration, and incorporation of hydrophobic units of HEC resulted in a slower gelation. The time of gelation for the dextran system was only slightly affected by the incorporation of hydrophobic groups (HM-dextran). At the gel point, a power law frequency dependence of the dynamic storage modulus (G' proportional to omegan') and loss modulus (G' proportional to omegan') was observed for all gelling systems with n' = n' = n. The attachment of hydrophobic moieties on the dextran chains had virtually no impact on the value of n (n = 0.77), and the percolation model describes the incipient dextran gels. By increasing the number of hydrophobic groups of the HEC polymer, the value of n for the corresponding incipient gel drops significantly, and the value of the gel strength parameter increases strongly. Incorporation of hydrophobic units in the HEC chains promotes the formation of stronger incipient gels because of the contribution from the hydrophobic association effect. The frequency dependence of the complex viscosity reveals that all the investigated gels become more solidlike in the postgel domain. Far into the postgel region, the hydrophobicity of HEC plays a minor role for the strength of the gel network, whereas the values of the complex viscosity are significantly higher for HM-dextran than for the corresponding dextran gel. The swelling experiments on HEC, HM-1-HEC, and HM-2-HEC systems disclose that the degree of swelling of the postgels in water is quite different, depending on the relative distance from the gel point at which the cross-linker reaction is quenched. At a given distance from the gel point, the swelling of the HEC gel is less pronounced than for the corresponding hydrophobically modified samples. At this stage, the swelling of the HM-dextran gel is stronger than for the dextran gel.     

Evaluation of agar and agarose gels for studying mechanical impedance in rice roots

Agar and agarose gels were evaluated as systems to mechanically impede roots of rice (Oryza sativa L.). Two-layer gels were used so that seedlings established in a layer of weak gel (0.35% weight/volume) and then grew downwards to encounter a treatment gel of up to 5.0% (w/v). Agarose gels were stronger than agar gels of the same concentration, reaching a maximum penetrometer resistance of 1.2 MPa at a concentration of 5.0%, compared to 0.3 MPa with agar. The 5.0% agar gel stimulated elongation of the seminal axis by 40% in seedlings of variety TN1 (compared with elongation in the 0.2% gel), but decreased it by 15% in the variety Lac 23. Although increasing agarose concentration decreased seminal axis elongation in both varieties, the seminal axis did not reach the lower layer of treatment gel when the concentration of the treatment gel was greater than 2.0%. The decreased root elongation was therefore a non-mechanical inhibition. In experiments conducted using a different batch of agarose, these inhibitory effects were not seen and strong agarose gels stimulated seminal axis elongation. It was concluded that the agar and agarose gel systems studied were unsuitable for studying the effect of mechanical impedance on the elongation of rice roots and that great care should be taken in interpreting the results of experiments using gels as a growth medium. This revised version was published online in June 2006 with corrections to the Cover Date.     

Isolation of the intercellular glycoproteins of desmosomes

To characterize the desmosome components that mediate intercellular adhesion and cytoskeletal-plasma membrane attachment, we prepared whole desmosomes and isolated desmosomal intercellular regions (desmosomal "cores") from the living cell layers of bovine muzzle epidermis. The tissue was disrupted in a nonionic detergent at low pH, sonicated, and the insoluble residue fractionated by differential centrifugation and metrizamide gradient centrifugation. Transmission electron microscopic analyses reveal that a fraction obtained after differential centrifugation is greatly enriched in whole desmosomes that possess intracellular plaques. Metrizamide gradient centrifugation removes most of the plaque material, leaving the intercellular components and the adjoining plasma membranes. Sodium dodecyl sulfate polyacrylamide gel electrophoresis coupled with methods that reveal carbohydrate-containing moieties on gels demonstrate that certain proteins present in whole desmosomes are glycosylated. These glycoproteins are specifically and greatly enriched in the desmosome cores of which they are the principal protein constituents, and thus may function as the intercellular adhesive of the desmosome.