ANALYSIS of Acid-Soluble Hydroxy-Proline,Free Proline and Collagen-Bound Hydroxyproline in Rat Liver by High Performance Liquid Chromatography With Pre-Column Derivatization

Abstract

A High Performance Liquid Chromatographic analysis of acid-soluble hydroxyproline, free proline and collagen-bound hydroxyproline from rat liver is described. A pre-column derivatisation with the fluorogenic reagent 7-chloro-4-nitrobenz-2-oxa-1,3-diazole was adopted. The Chromatographic assay was performed by using a Spherisorb ODS2 reversed phase column, with fluorometric detection. Elution was carried out isocratically with acetonitrile-O. 1 M sodium phosphate buffer, pH 7.2 (9:91, v/v). The derivatives of standard imino acids and of internal standard (3,4-dehydro-L-proline) can be separated in less than 15 min and quantitated with high sensitivity (1 injected pmole of hydroxyproline and 5 injected pinoles of proline). Key steps in the approach with the biological sample include initial extraction of acid-soluble hydroxyproline, free proline and collagen; acid hydrolysis of collagen and of hydroxyproline-containing peptides; selective derivatisation of imino acids with the fluoro-genic reagent, after a previous reaction of the sample with o-phthalaldehyde; finally, chromatographic analysis of the derivatives. The assay of acid-soluble hydroxyproline requires a clean-up step on a Sep-Pak C₁₈ cartridge prior to the analytical chromatography. Owing to its high sensitivity and reliability, the presented procedure can be used in studies on collagen metabolism and it should be preferred over the time-consuming and less sensitive colorimetric assays previously described.     

UVA- and UVB-induced changes in collagen and fibronectin biosynthesis in the skin of hairless mice.

The modifications induced in hairless mouse skin by chronic UV irradiation were investigated. Skin explant cultures were used to study UVA- and UVB-induced changes occurring in interstitial collagen (type I and type III) and fibronectin biosynthesis. To study the long-term effects, albino hairless mice were irradiated with UVA radiation alone from two sources with different spectral qualities or with UVB. UVA and UVB radiation produced a significant increase in the ratio of type III to type I collagen (more than 100% for UVA-irradiated skin and about 60% for UVB-irradiated skin) accompanied by a significantly increased fibronectin biosynthesis (50% or more in all irradiated groups). Irradiation with either UVA or UVB alone had no significant effect on the total collagen synthesis and resulted in only a slight decrease in the total collagen content of the skin determined as hydroxyproline. This decrease was significant only in the case of the group irradiated with UVA (xenon) (decrease of 25%, expressed as micrograms of hydroxyproline per milligram wet weight). A significant decrease in collagen hydroxylation (expressed as radioactive hydroxyproline/radioactive hydroxyproline plus proline in neosynthesized collagen) was observed of about 50% in skin irradiated with UVA (xenon) but not in UVB-treated skin. Several of the above modifications (increased fibronectin biosynthesis, increased collagen type III to type I ratio) correspond to the modifications observed during the aging of non-irradiated hairless mice. Therefore it appears that UV irradiation accelerates the modifications of extracellular matrix biosynthesis observed during aging.     

Separation of cyanogen bromide peptides of collagen by means of high-performance liquid chromatography

Cyanogen bromide peptides of bovine collagen Types I, II and III were analyzed using high-performance liquid chromatography (HPLC). Elution patterns of each collagen type were unique and reproducible.Elution patters of the CNBr peptides of the a1 and a2 chains of Type I collagen were also unique and together accounted for the major components of Type I collagen.Analysis of the eluted peptides from HPLC of each collagen type by sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed specific patterns for each collagen. Thus, unique and reproducible HPLC chromatograms were obtained, providing a new analytical method that is simple, sensitive and rapid.     

Hydroxyproline quantification for the estimation of collagen in tissue using multiple reaction monitoring mass spectrometry

Collagens are highly abundant mammalian proteins that contain a high content of hydroxylated amino acids such as hydroxyproline. We have exploited the high hydroxyproline content of collagen and developed a method for hydroxyproline quantification as a measure of collagen content in muscle samples. The novel method utilizes a highly selective and sensitive method of multiple reaction monitoring (MRM) by mass spectrometry. The analytical method is simple, rapid (5min), convenient (no derivatization), precise (<17% RSD), accurate (90-108%), sensitive (4.88nmol/L) and linear (R(2)>0.999) over three orders of magnitude (5-5000nmol/L).     

The effect of NDGA-modified etchant on the enzymatic degradation resistance and mechanical properties of collagen matrix

Bio-modified etchant can significantly improve the biostability of demineralized dentin collagen matrix, which validates the concept of etch-andcrosslink in dentin bonding.     

Analysis of type I and IV collagens by FT-IR spectroscopy and imaging for a molecular investigation of skeletal muscle connective tissue

Many muscular diseases result from abnormal organization of connective tissue and/or collagen network formation. Only a few molecular imaging techniques are able to analyze this collagen network by differentiating collagen types. In this study, FT-IR spectroscopy was used to analyze type I and IV collagens, the most important compounds of which are perimysium and endomysium, respectively. Secondary structure of collagen types was determined by curve-fitting the 1,700–1,480 cm⁻¹ spectral interval. Type I collagen could be differentiated from type IV by its higher amounts of triple helix and α-helix, but lower amounts of β-sheets (P < 0.01). FT-IR imaging was then used to determine structural features of perimysium and endomysium collagen network in bovine Flexor carpi radialis muscle. Secondary structure of proteins contained in perimysium and endomysium was found to be very close to type I and IV collagens, respectively. FT-IR spectroscopy and imaging are thus analytical tools that might be used for investigating biodistribution and assembly of collagen types in connective tissues. Figure Visible (left) and full spectral FT-IR (right) images of skeletal muscle tissue section (16 μm) exhibiting a vertical arrangement of fibers. + and × in FT-IR image show selected positions to obtain FT-IR spectra of perimysium and endomysium, respectively     

Chemie von α-Aminonitrilen 22. Mitteilung Regioselektive Synthese und Kristallstruktur von Uroporphyrinogen-(Typ I)-octanitril

Chemistry of α-Aminonitriles. Regioselective Synthesis and Crystal Structure of Uroporphyrinogen (Type I) Octanitrile A regioselective synthesis of uroporphyrinogen-octanitrile (type I) based on the strategy of multiple use of (dimethylmethylidene)ammonium iodide for stepwise regioselective functionalization of the pyrrole nucleus is described. This uroporphyrinogen derivative is remarkably stable and beautifully crystallizes in space group P1 with one molecule per unit cell. The crystal structure of the compound shows interesting conformational characteristics which are interpreted to be caused by subtle stereoelectronic effects. The English Footnotes to Schemes 1-3 and Figs. 1-12 provide an extension of this summary.     

柱前衍生高效液相色谱法对动物组织中胶原蛋白的测定

动物组织中的胶原蛋白经酸水解后生成包括羟脯氨酸在内的氨基酸混合物,用邻苯二甲醛（OPA）与其中的一级氨基酸衍生,再用9-芴基甲氧基羰酰氯（FMOC）与其中的羟脯氨酸衍生,用反相高效液相色谱法测定羟脯氨酸含量。羟脯氨酸是胶原蛋白的特异性氨基酸且含量稳定,因而可通过样品中羟脯氨酸的含量计算胶原蛋白含量。在0.01-50 mg.L^-1范围内,羟脯氨酸的峰面积和质量浓度之间的相关系数为0.9993,保留时间和峰面积的相对标准偏差分别为0.30%和2.9%。该法选用FMOC与氨基酸衍生产物的特征波长检测,能够完全屏蔽一级氨基酸衍生物的干扰,可快速、准确、高效地测定羟脯氨酸及胶原蛋白的含量。     

Spectrophotometric Determination of Cystine with O-Phthalaldehyde in the Absence of Thiol

Abstract

A spectrophotometric method for the determination of cystine with o-phthalaldehyde (OPA) in the absence of thiol is described. When cystine is heated at 60[ddot]C for 30 min in a low excess of OPA (pH 9.5), a very stable derivative with 1:2 stoichiometry (cystine:OPA) and an absorption maximum at 335 nm (E = 4600) is formed. At pH < 1 the derivative is protonated (protonation constants: log K¹ = 5.88 and log K² = 3.70 at I = 0.1 and 20[ddot]C) and another absorption band at 440 nm (E = 3800) appears, which allows the determination of cystine in the presence of other amino acids.     

An Improved Asymmetric Synthesis of Unusual Amino Acid (2S,3S)‐3‐Hydroxyproline

Abstract

An improved three‐steps method for the conversion of N‐benzyl (S)‐3‐hydroxypyrrolidin‐2‐one 6 to (2S,3S)‐3‐hydroxyproline 1 is reported. The key step is the reductive cyanation of 6. The synthesis of 1 constitutes a formal asymmetric synthesis of (2S,3S)‐3‐hydroxyproline betaines 2.     

Collagenase produced from Aspergillus sp. (UCP 1276) using chicken feather industrial residue

An extracellular collagenolytic serine protease was purified from Aspergillus sp., isolated from the Caatinga biome in northeast Brazil by a two‐step chromatographic procedure, using an anion‐exchanger and gel filtration. The enzyme was produced by submerged fermentation of feather residue as a substrate. The purified collagenase showed a 2.09‐fold increase in specific activity and 22.85% yield. The enzyme was a monomeric protein with a molecular mass of 28.7 kDa, estimated by an SDS–PAGE and AKTA system. The optimum temperature and pH for enzyme activity were around 40°C and pH 8.0, respectively. The enzyme was strongly inhibited by phenyl‐methylsulfonyl fluoride, a serine protease inhibitor, and was thermostable until 65°C for 1 h. We then evaluated the enzyme's potential for degradation of Type I and Type V collagens for producing peptides with antifungal activity. Our results revealed that the cleavage of Type V collagen yielded more effective peptides than Type I, inhibiting growth of Aspergillus terreus , Aspergillus japonicus and Aspergillus parasiticus . Both groups of peptides (Type I and Type V) were identified by SDS–PAGE. To conclude, the thermostable collagenase we purified in this study has various potentially useful applications in the fields of biochemistry, biotechnology and biomedical sciences.     

TYPE I AND TYPE II MECHANISMS IN THE PHOTOSENSITIZED LYSIS OF PHOSPHATIDYLCHOLINE LIPOSOMES BY HEMATOPORPHYRIN

Abstract The lysis of phosphatidylcholine (PC) liposomes was sensitized to visible light (>500nm) by hematoporphyrin (HP) incorporated in the liposomes (0.09-1.5%, wt/wt) or in the external buffer (1-15 μM). The lytic mechanism changed from the Type II pathway mediated by singlet oxygen (¹O₂) at low HP concentrations to the anoxic, Type I pathway at high HP concentrations. Spectral measurements of HP in aqueous and organic solvents indicate that the HP was not aggregated (monomers and/or dimers) for Type II sensitization and aggregated for Type I conditions. High concentrations of azide (>0.1 M) or DABCO (>0.5 M) were protective with high HP concentration under oxic and anoxic conditions, which cannot involve the scavenging of ¹O₂. Feasible protective mechanisms are quenching of the HP triplet state by high azide and repair of the damaged membrane by DABCO via an electron transfer process. There was significant protection against lysis under Type I conditions by low concentrations of ferricyanide (>1 mM), indicative of an electron transfer mechanism. The incorporation of 22 mol % cholesterol in PC liposomes with 1% HP had no effect on the lytic efficiency for oxic and anoxic conditions. Dipalmitoylphosphatidylcholine liposomes incorporating 1% HP showed negligible photosensitized lysis at 50°C compared with PC liposomes with 1% HP at 25°C. The promotion of photosensitized lysis by hydrodynamic agitation observed in prior work with methylene blue (Grossweiner and Grossweiner, 1982) was significant with HP sensitization for both Type I and Type II conditions. Actinometry with PC liposomes incorporating 1% HP indicated that photosensitized lysis was very inefficient, requiring many absorbed quanta per lysed liposome. Preliminary experiments with crude hematoporphyrin derivative (Hpd) showed similar concentration effects on lytic efficiency, where PC liposomes incorporating 0.1% (wt/wt) Hpd were strongly sensitized by oxygen, whereas sensitization by oxygen was insignificant with 3.1% Hpd. The results with HP and crude Hpd indicate that lytic damage in a biomembrane does not necessarily require oxygenation.     

Synthesis of Novel 2-(Pyridin-2-yl) Pyrimidine Derivatives and Study of Their Anti-Fibrosis Activity

A pyrimidine moiety exhibiting a wide range of pharmacological activities has been employed in the design of privileged structures in medicinal chemistry. To prepare libraries of novel heterocyclic compounds with potential biological activities, a series of novel 2-(pyridin-2-yl) pyrimidine derivatives were designed, synthesized and their biological activities were evaluated against immortalized rat hepatic stellate cells (HSC-T6). Fourteen compounds were found to present better anti-fibrotic activities than Pirfenidone and Bipy55′DC. Among them, compounds ethyl 6-(5-(p-tolylcarbamoyl)pyrimidin-2-yl)nicotinate (12m) and ethyl 6-(5-((3,4-difluorophenyl)carbamoyl)pyrimidin-2-yl)nicotinate (12q) show the best activities with IC₅₀ values of 45.69 μM and 45.81 μM, respectively. Furthermore, the study of anti-fibrosis activity was evaluated by Picro-Sirius red staining, hydroxyproline assay and ELISA detection of Collagen type I alpha 1 (COL1A1) protein expression. Our study showed that compounds 12m and 12q effectively inhibited the expression of collagen, and the content of hydroxyproline in cell culture medium in vitro, indicating that compounds 12m and 12q might be developed the novel anti-fibrotic drugs.     

Chemiluminescence Detection of Amino Acids,Peptides, and Proteins Using Tris-2,2′-Bipyridine Ruthenium (III)

Abstract

The feasibility of using the tris-2-2′-bipyridine ruthenium (III) (Ru(bpy)₃ ^{3 +}) chemiluminescent (CL) reaction for the detection of amino acids, peptides, and proteins has been studied.

Detection limits of the amino acids as determined by flow injection analysis (FIA) ranged from 20 pmol of proline to 50 nmol of asparagine. In general, amino acids containing secondary amine groups yielded the strongest responses. A reaction mechanism for Ru (bpy)₃ ^{3 +} chemiluminescence of aliphatic amines has been proposed. Studies of peptide molecules and poly-prolines showed that the peptide bond barely contributes to the detection signals. The separation of hydroxyproline and proline in synthetic collagen by HPLC with Ru (bpy)₃ ^{3 +} chemiluminescence detection has been shown to be possible.     

A new ligand-functionalizedβ-cyclodextrin as a esterolytic reagent at neutral pH

The paper reports the synthesis of a-cyclodextrin (-CD) derivative (1) functionalized with a ligand subunit at the secondary-hydroxyl rim. The ligand subunit is 2-hydroxymethyl-6-thiomethyl pyridine connected to the macrocycle via a thioether bond. In the presence of Cu(II) ions1 accelerates the cleavage of thep-nitrophenyl esters of picolinic acid (PNPP), quinaldic acid (PNPQ) and its 6-phenyl derivative (PNPQPh) via the nucleophilic attack of the hydroxyl of the pyridine subunit. However, the-CD derivative is less effective than the ligand 2-hydroxymethyl-6-methylthiomethyl pyridine (2), indicating no cooperation between the hydrophobic and metal ion recognition sites. However, in the case of PNPQPh, the observed rate constants in the presence of Cu(II) ions are close to that of model2 and this suggests we are approaching a binding mode appropriate for taking advantage of the two binding sites of the metal receptor1 · Cu(II). Interestingly, the most reactive derivative with native-CD is thep-nitrophenyl quinaldate (PNPQ) in accord with its mode of complexation to the macrocycle and the location of the actual nucleophile (one of the secondary hydroxyls of-CD).     

Pyridazine Derivatives and Related Compounds,Part 17: 1 The Synthesis of Some 3-Substituted Pyridazino[3′, 4′:3, 4]pyrazolo[5, 1-c]-1,2,4-triazines and Their Antimicrobial Activity

The reaction of the hydrazide of pyridazino[3′, 4′:3, 4]pyrazolo[5, 1-c]-1,2,4-triazine-3-carboxylic acid 3 with carbon disulfide in the presence of potassium hydroxide gave the 1,3,4-oxadiazole-2-thione derivative 4. The methylation of this product in an alkaline medium proceeds at the sulfur atom. The reaction of 3 with KOH and carbon disulfide followed by addition of hydrazine hydrate afforded the 4-amino-1,2,4-triazole derivative 6. Compound 3, when heated either with ammonium thiocyanate or with potassium thiocyanate, afforded the same product 7, which underwent cyclodehydration in the presence of acetyl chloride, which led to the 2-acetylamino-1,3,4-thiadiazole derivative 8. In a basic medium, the product was 1,2,4-triazole-3-thione derivative 9. The reaction of 3 with phenyl isothiocyanate provided thiosemicarbazide derivative 10, which underwent cyclodehydration in a basic medium and gave the 1,2,4-triazole derivative 11. The reaction of 3 with formic acid yielded the 3-carboxyl-2′-(formyl)hydrazine derivative 12. The refluxing of the latter with phosphorus pentasulfide in xylene yielded compound 14 (65%). The reaction of compound 12 with phosphorus pentoxide afforded compound 15. Some representative examples were screened for antimicrobial activity.     

Photoinitiators with Functional Groups 9: New Derivatives of Covalently Linked Benzophenone-amine Based Photoinitiators

As it had been shown that some covalently bound benzophenone (BP)—phenylglycine derivatives act as remarkable monomolecular Type II photoinitiators for radical polymerization, structural variations were investigated. The influence of the linking position between BP and the coinitiator and the coinitiator structure itself were considered. Furthermore, water soluble monomolecular BP-glycine based PIs were developed. While in UV-spectroscopy similar absorption behavior were found for all compounds, photo-DSC experiments revealed that derivative 2 has the most effective constitution.     

Impact of Dye‐Protein Interaction and Silver Nanoparticles on Rose Bengal Photophysical Behavior and Protein Photocrosslinking

The role of recombinant Type‐I human collagen in the free form or forming AgNP@collagen on the photophysical and photochemical behavior of rose Bengal was analyzed. The formation of dye aggregates on the protein surface was experimentally observed and corroborated by docking calculations. The formation of such aggregates is believed to change the main oxidative mechanism from Type‐II (singlet oxygen) to Type‐I (free radical) photosensitization. Remarkably, the presence of AgNP in the form of AgNP@collagen altered the dynamics of dye triplet deactivation, effectively preventing the dye degradation and reducing the extent of protein crosslinked. Both crosslinked rHC and AgNP@collagen were able to support fibroblasts proliferation, but only the material containing silver was resistant to S. epidermidis infection.