An oligosaccharide component in proteoglycans of articular cartilage.

Two types of sialic acid-containing component are released from articular cartilage proteoglycan monomer (D1) treated with 0.05 M NaOH containing 1 M NaBH4. The smaller component, which has not been described before, contains galactosamine, glucosamine, galactose and sialic acid (Molar ratio 1:1:1:2). It is eluted from ECTEOLA-cellulose with low molarity (0.4 M) sodium formate and has Kav of 0.70 on Bio-gel P30. Its presence on the proteoglycan monomer was demonstrated at all stages of foetal and adult life.     

An aminopeptidase from Streptomyces sp. KK565 degrades beta amyloid monomers, oligomers and fibrils

The accumulation of beta amyloid (Aβ) has been a primary target for Alzheimer disease therapeutic strategies. Previously, we discovered an activity from Streptomyces sp. KK565 growth media that inhibits Aβ aggregation. The active component was an aminopeptidase and named Streptomyces sp. KK565 aminopeptidase (SKAP). SKAP cleaved N-terminal amino-acids of Aβ_1-42 monomer, inhibited formation of fibrils and protected Aβ_1-42-induced neurotoxicity. Over-expression of a human homolog of SKAP, glutamate carboxypeptidase II (hGCPII) in Aβ-oversynthesizing cells dramatically reduced the Aβ levels. These findings suggest a possible role of M28 family peptidases in preventing Aβ deposits in mammalian brain.

Structured summary

MINT-7992796: SKAP (uniprotkb:Q306T3) physically interacts (MI:0915) with Abeta (uniprotkb:P05067) by protease assay (MI:0435)MINT-7992752, MINT-7992778: SKAP (uniprotkb:Q306T3) binds (MI:0407) to Abeta (uniprotkb:P05067) by protease assay (MI:0435)     

Behaviour of radioactive palmitic acid during heat treatment of bovine serum albumin

A radioactive complex AP_2.3 (A: bovine serum albumin, P: radioactive palmitic acid) has been prepared and incubated at pH 9 and 65°C for 60 min. Analysis by disc gel electrophoresis revealed three zones: zone 1, undenatured monomer; zone 1′, modified monomer; and zone 2, dimer. Counting of sliced gels indicated that only zone 1 was radioactive, meaning that fatty acids are released in the process 1→1′, but not in the process 1′+1′→2. In other words, fatty acids are released from albumin when native albumin is unfolded to form component 1′ during the incubation. The fatty acids released are concentrated on a particular species of albumin molecule which is not changed to component 1′. The percentage of component 1 (p) was 37%. This value agrees with that calculated by the equation which was proposed by us in a previous paper, p = (v/6) × 100%. In the present case v is 2.3.     

Structural Basis for the Recognition and Cleavage of Polysialic Acid by the Bacteriophage K1F Tailspike Protein EndoNF

An α-2,8-linked polysialic acid (polySia) capsule confers immune tolerance to neuroinvasive, pathogenic prokaryotes such as Escherichia coli K1 and Neisseria meningitidis and supports host infection by means of molecular mimicry. Bacteriophages of the K1 family, infecting E. coli K1, specifically recognize and degrade this polySia capsule utilizing tailspike endosialidases. While the crystal structure for the catalytic domain of the endosialidase of bacteriophage K1F (endoNF) has been solved, there is yet no structural information on the mode of polySia binding and cleavage available. The crystal structure of activity deficient active-site mutants of the homotrimeric endoNF cocrystallized with oligomeric sialic acid identified three independent polySia binding sites in each endoNF monomer. The bound oligomeric sialic acid displays distinct conformations at each site. In the active site, a Sia₃ molecule is bound in an extended conformation representing the enzyme-product complex. Structural and biochemical data supported by molecular modeling enable to propose a reaction mechanism for polySia cleavage by endoNF.     

Endothelial heparan sulphate: Compositional analysis and comparison of chains from different proteoglycan populations

From cultures of human umbilical vein endothelial cells incubated with³H-glucosamine or³⁵S-sulphate, we have purified three heparan sulphate proteoglycans: 1) a low density (1.31 g/ml) proteoglycan from the cell extract, 2) a low density proteoglycan from the medium, and 3) a high density (>1.4 g/ml) proteoglycan from the medium. The disaccharide composition of heparan sulphate chains from the low density proteoglycan of the medium was examined, using specific chemical and enzymic degradations followed by gel chromatography and strong anion exchange HPLC. Chains released from each of the different proteoglycan populations were then compared by gel chromatography and gradient polyacrylamide gel electrophoresis before and after various specific degradations. The results indicate that heparan sulphate from human endothelial cells are large polymers (MW>50,000) of low overall sulphation (32–35%N-sulphated glucosamine and an N/O-linked sulphate ratio of 2.0) with rare and solitary heparin-like disaccharides. Heparan sulphate from the different proteoglycan populations appeared to have similar structure except that chains from the high density fraction were larger polymers.Abbreviations HSPG heparan sulphate proteoglycan - DSPG dermatan sulphate proteoglycan - GlcNAc(6S) N-acetylglucosamine 6-sulphate - GlcNAc6R glucosamine with either-OH or-OSO₃ at C-6 - GlcNR glucosamine with either-SO₃ or-COCH₃ as N-substituent - GlcNSO₃ N-sulphated glucosamine - GlcNSO₃(3S) N-sulphated glucosamine 3-sulphate - GlcA d-glucuronic acid - IdoA l-iduronic acid - IdoA(2S) iduronic acid 2-sulphate - HexA hexuronic acid - DHexA hexuronic acid with a 4,5-double bond - Xyl xylose - SAX strong anion exchange - d.p. degree of polymerization (a disaccharide has d.p.=1 etc) - AUFS absorbance units full scale The codes used for proteoglycans denote in turn: C 2, low-density (1.35–1.28 g/ml) HSPG from the cell extract; M 1a, high density (>1.4 g/ml) HSPG fraction from the spent medium; M 2a, low-density (1.31 g/ml) HSPG from the spent medium [6].     

Isolation and characterization of proteoglycans from the swarm rat chondrosarcoma.

Proteoglycan monomer (D1) and aggregate (A1) preparations were isolated from 4 M guanidinium chloride extracts of the Swarm rat chondrosarcoma. When EDTA, 6-aminohexanoic acid, and benzamidine were present in the solutions, the D1 preparation contained a single component (SO = 23 S), and the A1 preparation contained 30% monomer (SO = 23 S) and 70 percent aggregate (SO = 111 S). In the absence of EDTA, 6-aminohexanoic acid, and benzamidine, the A1 preparations contained only small proteoglycan fragments, indicating that extensive enzymatic degradation had occurred. The composition of the proteoglycan monomer was different from that of proteoglycan monomer preparations from normal hyaline cartilages in that it did not contain keratan sulfate and chondroitin 6-sulfate; only chondroitin 4-sulfate was found. The A1 preparation from the chondrosarcoma contained only one link protein, which was like the smaller (molecular weight of 40,000) of the two link proteins present in A1 preparations from bovine nasal cartilage. When the A1 preparation from the chondrosarcoma was treated with chondroitinase ABC and trypsin and the digest was chromatographed on Sepharose 2B, a complex was isolated which contained the link protein and the segments of the protein core from the hyaluronic acid-binding region of the proteoglycan molecules.     

A comparison of methods for identifying the Jacobian for uncontrolled manifold variance analysis

Uncontrolled Manifold (UCM) analysis has been used to identify a component of joint variance leading to pointer-tip position variability and a component representing motor abundant joint combinations corresponding to an equivalent pointer-tip position. A Jacobian is required for UCM analysis, typically derived from an analytic model relating joint postures to pointer-tip position. Derivation of the Jacobian is often non-trivial, however, because of the complexity of the system being studied. In this article, we compared the effect of different methods of deriving the Jacobian on results of UCM analyses during reaching. Jacobian matrices were determined at each percentage of the reach across trials using one of three methods: (M1) partial derivatives of the geometric model relating ten joint postures, segment lengths and pointer length to the position of a hand-mounted pointer tip; or (M2–M3) as the coefficients of linear regression between the ten joint postures and either (M2) the pointer tip position measured directly from motion capture or (M3) the pointer-tip position estimated from the geometric model. For all methods, motor abundant joint variance (V_UCM) was larger than joint variance leading to a variable pointer-tip position (V_ORT). Results did not differ among methods prior to the time of peak velocity. Thereafter, M2 yielded lower V_ORT and slightly higher V_UCM compared to M1. Method M3 was used to disambiguate the possible effect of estimating model parameters for the geometric model on the M1–M2 comparison. The advantages of the use of linear regression method in the UCM approach are discussed.     

Determination of sialic acids in immune system cells (coelomocytes) of sea urchin,Paracentrotus lividus,using capillary LC-ESI-MS/MS

Coelomocytes are considered to be immune effectors of sea urchins. Coelomocytes are the freely circulating cells in the body fluid contained in echinoderm coelom and mediate the cellular defence responses to immune challenges by phagocytosis, encapsulation, cytotoxicity and the production of antimicrobial agents. Coelomocytes have the ability to recognize self from non-self. Considering that sialic acids play important roles in immunity, we determined the presence of sialic acid types in coelomocytes of Paracentrotus lividus. Homogenized coelomocytes were kept in 2 M aqueous acetic acid at 80 °C for 3 h to liberate sialic acids. Sialic acids were determined by derivatization with 1,2-diamino-4,5-methylenediaoxy-benzene dihydrochloride (DMB) followed by capillary liquid-chromatography-electrospray ionization/tandem mass spectrometry (CapLC-ESI-MS/MS). Standard sialic acids; Neu5Ac, Neu5Gc, KDN and bovine submaxillary mucin showing a variety of sialic acids were used to confirm sialic acids types. We found ten different types of sialic acids (Neu5Gc, Neu5Ac, Neu5Gc9Ac, Neu5Gc8Ac, Neu5,9Ac₂, Neu5,7Ac₂, Neu5,8Ac₂, Neu5,7,9Ac₃, Neu5Gc7,9Ac₂, Neu5Gc7Ac) isolated in limited amounts from total coelomocyte population. Neu5Gc type of sialic acids in coelomocytes was the most abundant type sialic acid when compared with other types. This is the first report on the presence of sialic acid types in coelomocytes of P. lividus using CapLC-ESI-MS/MS-Ion Trap system (Capillary Liquid Chromatography-Electrospray Ionization/Tandem Mass Spectrometry).     

D-aspartate oxidase in mammalian brain and choroid plexus

Abstract— Synaptosomes from guinea-pig cerebral cortex contain a fetuin: sialyl glyco-protein: glycosyl transferase; evidence is presented which indicates that both a sialyl transferase; evidence is presented which indicates that both a sialyl transferase and endogenous acceptors were located in the synaptosome ‘ghost’ fractions. Following solubilization of synaptosomes with Triton X-100 and the use of fetuin minus NANA as acceptor, 25 per cent of the transferase was recovered after centrifugation and column chromatography on Sephadex G-100 and G-200 with a 64·0-fold purification. The enzyme had a pH optimum of 6·3, required no divalent metal cation for activity, and exhibited high activity with either fetuin minus sialic acid, prothrombin minus sialic acid, Tamm-Horsfall glycoprotein minus sialic acid, or orosomucoid minus sialic acid as acceptor; neither BSM nor PSM minus NANA functioned as an effective acceptor. The fetuin:sialyl transferase using fetuin minus sialic acid and CMP-sialic acid as substrates a and b, respectively, gave the following kinetic constants when using the Cleland bisubstrate model: K_a= 35μM; K_b= 3 μM; K_ia, = 25 μM; K_ib= 25μM; and V₁= 92 pmoles. min^?1.mg^?1 of protein. The following divalent cations inhibited the reaction: Ba²⁺ > Hg²⁺ > Pb²⁺ > Cu²⁺.     

Novel structural insights into rotavirus recognition of ganglioside glycan receptors

Rotaviruses ubiquitously infect children under the age of 5, being responsible for more than half a million diarrhoeal deaths each year worldwide. Host cell oligosaccharides containing sialic acid(s) are critical for attachment by rotaviruses. However, to date, no detailed three-dimensional atomic model showing the exact rotavirus interactions with these glycoconjugate receptors has been reported. Here, we present the first crystallographic structures of the rotavirus carbohydrate-recognizing protein VP8^? in complex with ganglioside G_M3 glycans. In combination with assessment of the inhibition of rotavirus infectivity by N-acetyl and N-glycolyl forms of this ganglioside, our results reveal key details of rotavirus-ganglioside G_M3 glycan recognition. In addition, they show a direct correlation between the carbohydrate specificities exhibited by VP8^? from porcine and by monkey rotaviruses and the respective infectious virus particles. These novel results also indicate the potential binding interactions of rotavirus VP8^? with other sialic acid-containing gangliosides.     

Comparison of the 13C-n.m.r. spectra of gangliosides GM1 with those of GM1-oligosaccharide and asialo-GM1

The ¹³C-n.m.r. spectra of asialo-G_M1 and G_M1-oligosaccharide are completely assigned and compared to those previously found for intact G_M1 and for the series G_M4, G_M3, G_M2, G_M1, G_D1a, G_D1b, and G_T1b. Removal of the ceramide residue from G_M1 liberated a free, reducing aldehyde group, which was reflected in a doubling of the ¹³C-n.m.r. signals assignable to the d-glucose residue because of α,β equilibrium. The spectrum of asialo-G_M1 lacks the resonances from the sialic acid residue, as expected; in addition, several resonances from the neutral gangliotetraglycosyl residue shifted to different field positions after removal of sialic acid from G_M1. These resonances include that of C-4 of the inner β-d-galactosyl residue, and C-1 of the 2-acetamido-2-deoxy-d-galactosyl residue that is near the site of attachment of the sialosyl residue. The differences between the chemical shifts of the carbon resonances of oligomeric and monomeric saccharides, termed linkage shifts, provide a quantitative assignment aid. They are ～ $\text{1}\text{3}$ of those for residues linked to sialic acid than those for residues linked to the neutral hexose chain. Correlations among linkage shifts for pairs of glycosidically-linked carbon atoms for asialo-G_M1 and G_M1-oligosaccharide were compared with those for the series of gangliosides G_M4 to G_T1b, and differences are noted for resonances for carbon atoms near the sialic acid residue. The spectrum of ganglioside G_M1b, a positional isomer of G_M1 whose ¹³C-n.m.r. spectrum has not yet been observed, is predicted.     

Inhibition effect of flavonoid compounds against neuraminidase expressed in Pichia pastoris

Neuraminidase (NA) is one of the two glycoproteins on the surface of influenza virus, which cleaves terminal sialic acid residues and facilitates the release of virions from infected cells. The recombinant NA from H5N1 influenza virus strain A/Vietnam/1203/04 was expressed in Pichia pastoris X33 as a 45 kDa protein that displayed a K _m of 9.96 ± 1.26 μM with fluorogenic substrate, 2′-(4-methylumbelliferyl)-α-D-N-acetyl neuraminic acid. Partially purified NA was used for the inhibition and kinetic assays with eight flavonoid compounds and gallic acid. Among them, gallocatechin gallate (GCG) showed the best inhibition against NA with the IC₅₀ of 8.98 ± 0.46 μM and showed a competitive inhibition pattern with K _i value of 8.34 ± 0.25 μM. In molecular docking experiments, GCG displayed a binding energy of ?13.71 kcal/mol to the active site of NA and the galloyl moiety was required for NA inhibition activity.     

Tissue distribution of EDTA encapsulated within liposomes containing glycolipids or brain phospholipids

Multilamellar liposomes were prepared with various asialoglycolipids, gangliosides, sialic acid, or brain phospholipids in the liposome membrane and with ethylenediaminetetraacetic acid (EDTA) encapsulated in the aqueous compartments. The liposomes containing glycolipids or sialic acid were prepared from a mixture of phosphatidylcholine, cholesterol, and one of the following test substances: galactocerebroside, glucocerebroside, galactocerebroside sulfate, mixed gangliosides, monosialoganglioside G_M1, monosialoganglioside G_M2, monosialoganglioside G_M3, disialoganglioside G_D1a, or sialic acid. The liposomes containing brain phospholipids were mixtures of either sphingomyelin and cholesterol or a brain total phospholipid extract and cholesterol. Distribution of ¹⁴C-labeled EDTA were determined in mouse tissues from 15 min to 6 h or 12 h after a single injection of liposome prepartion. Liver uptake of encapsulated EDTA was lowest from all liposome preparations containing sialic acid or sialogangliosides regardless of the amount of sialic acid moiety present or the identity of the particular ganglioside; highest uptake of encapsulated EDTA by liver was from the liposomes containing galactocerebroside or brain phospholipids. Lungs and brain took up the largest amounts of EDTA from liposomes containing sphingomyelin and lesser amounts from liposomes containing G_D1a. Use of mouse brain phospholipid extract to prepare liposomes did not increase uptake of encapsulated EDTA by the brain. EDTA in liposomes containing monosialogangliosides, brain phospholipids, galactocerebroside, or sialic acid was taken up well by spleen and marrow. Highest thymus uptake of encapsulated EDTA was from liposomes containing G_D1a. These results demonstrate that inclusion of sialogangliosides in liposome membranes decreases uptake of liposomes by liver, thus making direction of encapsulated drugs to other organs more feasible. Liposomes containing glycolipids also have potential uses as probes of cell surface receptors.     

Physical and immunochemical properties of low-buoyant-density proteoglycans from avian cartilage

A proteoglycan link fraction (A₁D₅) from avian xyphoid cartilage contains one link protein and low-buoyant-density proteoglycans. An antiserum made against this fraction (anti-A₁D₅ serum) specifically binds [³⁵S]sulfate-labeled proteoglycans from aggregate (A₁), monomer (A₁D₁), and link (A₁D₅) fractions synthesized by 14-day embryonic chick sterna. When [³⁵S]sulfate-labeled proteoglycans from either monomer (A₁D₁) or link (A₁D₅) fractions are used as the antigen, anti-A₁D₅ serum binds as well as an antiserum against a purified monomer preparation (anti-A₁D₁1400 Vo serum). However, reduction and alkylation of the proteoglycans from the monomer fraction does reveal differences in the binding of the two antisera. Whereas reduction and alkylation of the antigen (³⁵S-A₁D₁) inhibit binding by both antisera, binding of the anti-A₁D₅ serum is more affected by antigen alteration. Differences in the two antisera can also be detected in assays using labeled aggregate as antigen. Anti-A₁D₅ serum cannot maintain the same levels of antigen binding as the anti-A₁D₁-1400 Vo serum when compared in an antibody dilution curve. In addition, anti-A₁D₁-1400 Vo serum can stabilize aggregate during sedimentation in a sucrose density gradient containing 4 m guanidine hydrochloride whereas anti-A₁D₅ serum cannot. These results suggest that the low-buoyant-density proteoglycans found in the link (A₁D₅) fraction from avian cartilage contain some of the antigenic determinants found on the proteoglycan monomer. However, there is at least one monomer determinant which is not present in the A₁D₅ fraction.     

Purification, Characterization, and Crystallization of the Components of the Nitrobenzene and 2-Nitrotoluene Dioxygenase Enzyme Systems

The protein components of the 2-nitrotoluene (2NT) and nitrobenzene dioxygenase enzyme systems from Acidovorax sp. strain JS42 and Comamonas sp. strain JS765, respectively, were purified and characterized. These enzymes catalyze the initial step in the degradation of 2-nitrotoluene and nitrobenzene. The identical shared reductase and ferredoxin components were monomers of 35 and 11.5 kDa, respectively. The reductase component contained 1.86 g-atoms iron, 2.01 g-atoms sulfur, and one molecule of flavin adenine dinucleotide per monomer. Spectral properties of the reductase indicated the presence of a plant-type [2Fe-2S] center and a flavin. The reductase catalyzed the reduction of cytochrome c, ferricyanide, and 2,6-dichlorophenol indophenol. The ferredoxin contained 2.20 g-atoms iron and 1.99 g-atoms sulfur per monomer and had spectral properties indicative of a Rieske [2Fe-2S] center. The ferredoxin component could be effectively replaced by the ferredoxin from the Pseudomonas sp. strain NCIB 9816-4 naphthalene dioxygenase system but not by that from the Burkholderia sp. strain LB400 biphenyl or Pseudomonas putida F1 toluene dioxygenase system. The oxygenases from the 2-nitrotoluene and nitrobenzene dioxygenase systems each had spectral properties indicating the presence of a Rieske [2Fe-2S] center, and the subunit composition of each oxygenase was an α₃β₃ hexamer. The apparent K_m of 2-nitrotoluene dioxygenase for 2NT was 20 μM, and that for naphthalene was 121 μM. The specificity constants were 7.0 μM⁻¹ min⁻¹ for 2NT and 1.2 μM⁻¹ min⁻¹ for naphthalene, indicating that the enzyme is more efficient with 2NT as a substrate. Diffraction-quality crystals of the two oxygenases were obtained.     

Reconstitution in vitro of the catalytic portion (NtpA3-B3-D-G complex) of Enterococcus hirae V-type Na-ATPase

Enterococcus hirae vacuolar ATPase (V-ATPase) is composed of a soluble catalytic domain (V₁; NtpA₃-B₃-D-G) and an integral membrane domain (V₀; NtpI-K₁₀) connected by a central and peripheral stalk(s) (NtpC and NtpE-F). Here we examined the nucleotide binding of NtpA monomer, NtpB monomer or NtpD-G heterodimer purified by using Escherichia coli expression system in vivo or in vitro, and the reconstitution of the V₁ portion with these polypeptides. The affinity of nucleotide binding to NtpA was 6.6 μM for ADP or 3.1 μM for ATP, while NtpB or NtpD-G did not show any binding. The NtpA and NtpB monomers assembled into NtpA₃-B₃ heterohexamer in nucleotide binding-dependent manner. NtpD-G bound NtpA₃-B₃ forming V₁ (NtpA₃-B₃-D-G) complex independent of nucleotides. The V₁ formation from individual NtpA and NtpB monomers with NtpD-G heterodimer was absolutely dependent on nucleotides. The ATPase activity of reconstituted V₁ complex was as high as that of native V₁-ATPase purified from the V₀V₁ complex by EDTA treatment of cell membrane. This in vitro reconstitution system of E. hirae V₁ complex will be valuable for characterizing the subunit-subunit interactions and assembly mechanism of the V₁-ATPase complex.     

Four-α-Helix Bundle with Designed Anesthetic Binding Pockets. Part II: Halothane Effects on Structure and Dynamics

As a model of the protein targets for volatile anesthetics, the dimeric four-α-helix bundle, (Aα₂-L1M/L38M)₂, was designed to contain a long hydrophobic core, enclosed by four amphipathic α-helices, for specific anesthetic binding. The structural and dynamical analyses of (Aα₂-L1M/L38M)₂ in the absence of anesthetics (another study) showed a highly dynamic antiparallel dimer with an asymmetric arrangement of the four helices and a lateral accessing pathway from the aqueous phase to the hydrophobic core. In this study, we determined the high-resolution NMR structure of (Aα₂-L1M/L38M)₂ in the presence of halothane, a clinically used volatile anesthetic. The high-solution NMR structure, with a backbone root mean-square deviation of 1.72 Å (2JST), and the NMR binding measurements revealed that the primary halothane binding site is located between two side-chains of W15 from each monomer, different from the initially designed anesthetic binding sites. Hydrophobic interactions with residues A44 and L18 also contribute to stabilizing the bound halothane. Whereas halothane produces minor changes in the monomer structure, the quaternary arrangement of the dimer is shifted by about half a helical turn and twists relative to each other, which leads to the closure of the lateral access pathway to the hydrophobic core. Quantitative dynamics analyses, including Modelfree analysis of the relaxation data and the Carr-Purcell-Meiboom-Gill transverse relaxation dispersion measurements, suggest that the most profound anesthetic effect is the suppression of the conformational exchange both near and remote from the binding site. Our results revealed a novel mechanism of an induced fit between anesthetic molecule and its protein target, with the direct consequence of protein dynamics changing on a global rather than a local scale. This mechanism may be universal to anesthetic action on neuronal proteins.     

Determination os sedimentation coefficient distributions for cartilage proteoglycans

Sedimentation coefficient distributions of widely polydisperse proteoglycan preparations were made using a previously developed transport sedimentation methodology. Boundary stability was improved by centrifuging samples in a preformed CsCl density gradient (0.016 g/cm⁴). The results were compared with the distributions obtained with an interferometric analytical centrifugation method. When these two techniques were applied to analyze A1 and A1–D1 proteoglycan preparations, results were in substantial agreement with respect to the mean sedimentation coefficients of the peaks, average S value, sedimentation coefficient distribution, skewness, proportion of monomer and aggregates, and linearity of the plot ln(s) versus C extrapolations to zero concentration. The lower solute concentration compatible with the transport (velocity gradient) method makes this technique particularly suitable for studying the details of proteoglycan distribution of molecular sizes, especially for aggregates.     

Physicochemical properties of cartilage proteoglycans extracted by lanthanum chloride

Bovine nasal cartilage was extracted with 0.5 M LaCl₃ and the extract then diluted with nine volumes of water. The resulting precipitate (P_LaCl3) contained the proteoglycan subunits, together with minor protein components, but was essentially free from hyaluronic acid. The properties of P_LaCl3 were investigated by chemical analysis, electrophoresis, viscometry and analytical ultracentrifugation, and the results compared with those for proteoglycan obtained by caesium chloride density gradient centrifugation of 2 M CaCl₂ cartilage extracts. Proteoglycan subunits (A1D1) prepared from P_LaCl3 showed identical properties to those obtained from other high ionic strength cartilage extracts.