Calf Skin Collagen Research Articles

Structural properties of pepsin-solubilized collagen acylated by lauroyl chloride along with succinic anhydride.

The structural properties of pepsin-solubilized calf skin collagen acylated by lauroyl chloride along with succinic anhydride were investigated in this paper. Compared with native collagen, acylated collagen retained the unique triple helix conformation, as determined by amino acid analysis, circular dichroism and X-ray diffraction. Meanwhile, the thermostability of acylated collagen using thermogravimetric measurements was enhanced as the residual weight increased by 5%. With the temperature increased from 25 to 115 °C, the secondary structure of native and acylated collagens using Fourier transform infrared spectroscopy measurements was destroyed since the intensity of the major amide bands decreased and the positions of the major amide bands shifted to lower wavenumber, respectively. Meanwhile, two-dimensional correlation spectroscopy revealed that the most sensitive bands for acylated and native collagens were amide I and II bands, respectively. Additionally, the corresponding order of the groups between native and acylated collagens was different and the correlation degree for acylated collagen was weaker than that of native collagen, suggesting that temperature played a small influence on the conformation of acylated collagen, which might be concluded that the hydrophobic interaction improved the thermostability of collagen.

Isolation and characterization of collagen from the body wall of sea cucumber Stichopus monotuberculatus.

To exploit a new collagen resource from the body wall of tropical sea cucumber, pepsin-solubilized collagen of Stichopus monotuberculatus (PSC-Sm) was isolated and characterized with UV-vis spectra, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), amino acid composition, enzyme-digested peptide maps, Fourier transform infrared spectroscopy (FTIR), maximum transition temperature (Tm ), and solubilities. The maximum absorbance of PSC-Sm was exhibited at 218 nm in UV-vis spectra. The triple helical structure and activity of PSC-Sm could be indicated by FTIR. SDS-PAGE showed that the triple helix of PSC-Sm was formed as (α1 )3 by 3 α1 chain homologous with molecular weight of 137 kDa. The Tm of PSC-Sm and calf skin collagen (CSC) were 30.2 and 35.0 ºC, respectively, which consistent with the result of FTIR that CSC contained more stable triple-helix than PSC-Sm. Peptide maps were different between PSC-Sm and CSC, indicating the differences in their amino acid compositions and sequences. The maximum and minimum solubilities of PSC-Sm were observed at pH 2.0 and 4.0, respectively. A sharp decrease in solubility appeared when NaCl concentration was between 3% and 5%. These results showed that collagen from S. monotuberculatus had the type I collagen characteristics and good thermal stability, and therefore, it could be used as an alternative resource of collagen.

Characteristics of Gelatin from Giant Grouper (Epinephelus Lanceolatus) Skin

Gelatin extraction from the skin of giant grouper (Epinephelus lanceolatus) was conducted by acid process with a yield of 20.27 g/100 g wet skin sample. The characteristics of extracted gelatin from giant grouper was investigated in this study, and further compared to that from commercial tilapia. Results showed that when compared to commercial tilapia, giant grouper had lower levels of bloom strength and foam formation ability, but greater values of viscosity, foam stability, and lightness (L*) on gelatin skin. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis revealed three high-bands intensities of major protein components of giant grouper skin gelatin, representing α1-chain, α2-chain, and β-components, and was similar to that of standard calf skin collagen type I. Compared to giant grouper, commercial tilapia contained extra proteins with molecular weight less than 70 kDa on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis of both skin gelatins.

Thermal and Photochemical Effects on the Fluorescence Properties of Type I Calf Skin Collagen Solutions at Physiological pH

Mammalian collagens exhibit weak intrinsic UV fluorescence that depends on the age and previous history of the sample. Post-translational modifications result in additional fluorescent products (e.g. DOPA, dityrosine, and advanced glycation end products (AGE)). UV radiation can cause longer wavelength fluorescent oxidative bands. These alterations can assess the extent of photolysis. We describe the ground- and excited-state oxidative transformations of newly-purchased type I calf skin collagens (samples #092014 and #072012) and a 7-year-old sample (#072005). We compare the effects of UV radiation (mainly 254 nm) and age on the photochemical reaction kinetics and fluorescence spectral distribution of type I calf skin collagen at pH 7.4. The fluorescence spectra of samples #072012 and #092014 were similar but not identical to pure tyrosine, whereas #072005 indicated significant “dark” oxidation at the expense of tyrosine. Fading of oxidized product(s) at 270/360 nm is second-order. Build-up of 325/400 nm (dityrosine) fluorescence is linear with time. Rate parameters r2 and r1 were respectively proportional to second order disappearance of ground state oxidation products and the quasi–first-order photochemical formation of dityrosine. There is a reciprocal relationship between the rates of decrease in the 270/360 nm fluorescence and concomitant increase in 325/400 nm fluorescence. Their relative rates depend on the age of the collagen sample. There is a reciprocal relationship between r1 and r2. This relationship results because both ground state autoxidation and excited state photo-dimerization proceed via a common tyrosyl radical intermediate. Water of hydration appears to play a role in generating tyrosyl radical.

Novel synthesis and characterization of a collagen-based biopolymer initiated by hydroxyapatite nanoparticles

In this study, we developed a novel synthesis method to create a complex collagen-based biopolymer that promises to possess the necessary material properties for a bone graft substitute. The synthesis was carried out in several steps. In the first step, a ring-opening polymerization reaction initiated by hydroxyapatite nanoparticles was used to polymerize d,l-lactide and glycolide monomers to form poly(lactide-co-glycolide) co-polymer. In the second step, the polymerization product was coupled with succinic anhydride, and subsequently was reacted with N-hydroxysuccinimide in the presence of dicyclohexylcarbodiimide as the cross-linking agent, in order to activate the co-polymer for collagen attachment. In the third and final step, the activated co-polymer was attached to calf skin collagen type I, in hydrochloric acid/phosphate buffer solution and the precipitated co-polymer with attached collagen was isolated. The synthesis was monitored by proton nuclear magnetic resonance, infrared and Raman spectroscopies, and the products after each step were characterized by thermal and mechanical analysis. Calculations of the relative amounts of the various components, coupled with initial dynamic mechanical analysis testing of the resulting biopolymer, afforded a preliminary assessment of the structure of the complex biomaterial formed by this novel polymerization process.

Purification and Characterization of Pepsin-Solubilized Collagen from Skin of Sea Cucumber Holothuria parva

Pepsin-solubilized collagen (PSC) was extracted from the skin of sea cucumber Holothuria parva and was fractionally characterized. The PSC from H. parva skin consisted of three α1 chains (α1)3, in contrast to calf skin collagen type I with two α1 and one α2 chains (α1)2α2 with approximately 130kDa each. The maximum transition (Tm) and denaturation temperature (Td) of PSC were determined to be 46.94 and 32.5°C, respectively. The amino acid composition analysis revealed that glycine, proline, alanine, and hydroxyproline were the abundant amino acids available in extracted PSC. The results showed that the isolated collagen from H. parva has some similar characteristics to previously reported collagens used in food and pharmaceutical industries.

Characterization of Acid-soluble Collagen from the Skin of Hammerhead Shark (Sphyrna lewini )

The characteristics of the acid-soluble collagen (ASC) from the skin of hammerhead shark (Sphyrna lewini) (ASC-H) were investigated and compared with those of calf skin collagen (CSC). ASC-H with a yield of 4.23 ± 0.54% (based on the wet weight of skins) contained Gly (227 residues/1,000 residues) as the major amino acid and had imino acids of 205 residues/1,000 residues. Amino acid composition, sodium dodecyl sulfate polyacrylamide gel electrophoresis pattern and Fourier transform spectroscopy (FTIR), confirmed that ASC-H was mainly composed of type I collagen. The peptide map of ASC-H was different from that of CSC, suggesting the differences in amino acid sequences and conformation. Td of ASC-H was 16.89C, which was similar to those of cold-water fishes but significantly lower than those of tropical fish species and mammals. ASC-H exhibited high solubility in pH (1-4) and low NaCl concentrations (≤3%). In addition, the lyophilized collagen displayed loose, fibrous and porous ultrastructure. Practical Applications At present, large quantities of by-products, accounting for 50–70% of the original raw material, are generated during the process of aquatic products processing industry. Therefore, optimal use of these by-products is a promising way to protect the environment and produce value-added products to increase the revenue of fish processors. Recently, many scientists have focused their interests on isolation and characterization of collagens extracted from skins of aquatic organisms. However, no information regarding acid-soluble collagen (ASC) from skins of Hammerhead shark (Sphyrna lewini) has been reported. The aim of this study was to isolate and characterize ASC from skin of Hammerhead shark in comparison with type I collagen from calf skin (CSC). Therefore, the collagen extracted from the skin of hammerhead shark could bring considerably economic benefits as a substitute for mammalian collagen.

Characterization of Acid-Soluble Collagen From Bone of Pacific Cod (Gadus macrocephalus)

Acid-soluble collagen (ASC) was isolated from Pacific cod (Gadus macrocephalus) bone. The ASC was rich in glycine. The amount of imino acid was lower than that of calf skin collagen, as was the transition temperature (48.6°C). Electrophoresis revealed two different α chains (α1 and α2), β-component, and γ-component. Fourier transform infrared spectroscopy measurement showed that ASC was in triple-helix structure. ASC had a solubility greater than 90% in a very acidic pH range (pH 1–4), and the solubility decreased with increasing NaCl concentrations up to 3%. Lyophilized ASC had a network ultrastructure with lace-like fibers, similar to calf skin collagen sponge.

Characterization of acylated pepsin-solubilized collagen with better surface activity

A new kind of acylated collagen with water solubility and better surface activity was prepared via reaction of pepsin-solubilized calf skin collagen with lauroyl chloride and succinic anhydride in this paper. The equilibrium surface tension and the isoelectric point were 55.92mN/m and 4.93 respectively, suggesting that acylated collagen had surface activity as well as water solubility. Meanwhile, the results of Fourier transform infrared spectroscopy analyses and electrophoresis patterns demonstrated that the triple helix conformation of collagen was not destroyed, but the subunits of acylated collagen shifted to higher molecular weight than those of native collagen. Scanning electron microscope and differential scanning calorimeter measurements revealed that lyophilized acylated collagen exhibited relatively well-distributed pore structure and its denaturation temperature was about 9.0°C higher than that of native collagen. Additionally, the increase of the diameter of the fibrils was observed by atomic force microscopy. Acylated collagen with water solubility and better surface activity might broaden the application of collagen-based materials to cosmetics, drug delivery and pharmacotherapy.

Biochemical and thermo-mechanical analysis of collagen from the skin of Asian Sea bass (Lates calcarifer) and Australasian Snapper (Pagrus auratus), an alternative for mammalian collagen

Australasia has a large fish industry, and fish skin by-products from the processing industry could be used for the commercial production of fish collagen. The aim of this study was to characterize collagen extracted from the Asian sea bass (Australian barramundi) (Lates calcarifer) and snapper (Pagrus auratus) skin as an alternative to mammalian-derived collagen in gelatin products. The acid-soluble fractions of collagen from Asian sea bass and snapper skin were extracted and yielded about 8 and 7.5 % collagen (on a dry weight basis), respectively. The electrophoretic and chromatography patterns indicated that both collagens comprise of α1, α2, α3, and β chains, corresponding to the properties of calf skin collagen type I. Amino acid analysis and peptide mapping of digested collagen suggested differences in their amino acid sequences and collagen primary structure. Fourier transform infrared spectroscopy demonstrated that the helical structure of collagen was completely maintained in Asian sea bass and partially in snapper. Transition temperatures for the completion of the melting process in the two collagen networks were confirmed with differential scanning calorimetry and dynamic oscillatory rheology to be about 29 °C. Zeta potential analysis identified the isoelectric points (pI values) of collagen from Asian sea bass and snapper skin at pH 6.90 and 7.75, respectively. Thus, Asian sea bass and snapper skin could be an important alternative source of collagen to replace mammalian collagen for industrial applications.

Angiogenic gene-modified myoblasts promote vascularization during repair of skeletal muscle defects

Vascularization is thought to be a principle obstacle in the reconstruction of skeletal muscle defects. Long-term survival of reconstructed skeletal muscle is dependent on good vascularization. In this study, we upregulated angiogenic gene expression in myoblasts in an attempt to promote vascularization during repair of skeletal muscle defects. Skeletal myoblasts were isolated and expanded from newborn male Sprague-Dawley (SD) rats. The cells were transfected with human vascular endothelial growth factor 165 (VEGF-165) or human stromal cell-derived factor 1 (SDF-1), using Lipofectamine™ 2000 transfection reagent, prior to seeding onto calf collagen scaffolds. Gene and protein overexpression was verified by ELISA, RT-PCR and western blot analysis. Cell-seeded scaffolds were transplanted into back muscle defects in female SD rats. At weeks 2, 4 and 8 after transplantation, Y chromosome detection was used to observe the survival of growth factor-producing cells within the scaffolds in vivo. Capillary density was investigated using microvessel density detection, haematoxylin and eosin (H&E) staining and immunohistochemical staining. We found that vascularization was enhanced by transfected myoblasts compared with non-transfected myoblasts. In addition, VEGF-165 and SDF-1 had a synergistic effect on vascularization during repair of skeletal muscle defects in vivo. In conclusion, we have combined myoblast-seeded collagen sponge with gene therapy, resulting in a promising approach for the construction of well-vascularized skeletal muscle.

Resemblance of Electrospun Collagen Nanofibers to Their Native Structure

Electrospinning is a promising method to mimic the native structure of the extracellular matrix. Collagen is the material of choice, since it is a natural fibrous structural protein. It is an open question how much the spinning process preserves or alters the native structure of collagen. There are conflicting results in the literature, mainly due to the different solvent systems in use and due to the fact that gelatin is employed as a reference state for the completely unfolded state of collagen in calculations. Here we used circular dichroism (CD) and Fourier-transform infrared spectroscopy (FTIR) to investigate the structure of regenerated collagen samples and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to illuminate the electrospun nanofibers. Collagen is mostly composed of folded and unfolded structures with different ratios, depending on the applied temperature. Therefore, CD spectra were acquired as a temperature series during thermal denaturation of native calf skin collagen type I and used as a reference basis to extract the degree of collagen folding in the regenerated electrospun samples. We discussed three different approaches to determine the folded fraction of collagen, based on CD spectra of collagen from 185 to 260 nm, since it would not be sufficient to obtain simply the fraction of folded structure θ from the ellipticity at a single wavelength of 221.5 nm. We demonstrated that collagen almost completely unfolded in fluorinated solvents and partially preserved its folded structure θ in HAc/EtOH. However, during the spinning process it refolded and the PP-II fraction increased. Nevertheless, it did not exceed 42% as deduced from the different secondary structure evaluation methods, discussed here. PP-II fractions in electrospun collagen nanofibers were almost same, being independent from the initial solvent systems which were used to solubilize the collagen for electrospinning process.

The Synthesis and Characterization of Nano-hydroxyapatite (nHAP)-g-poly(lactide-co-glycolide)-g-collagen Polymer for Tissue Engineering Scaffolds

ABSTRACTBone grafts, commonly performed to augment bone regeneration from autologous or alleogeneic sources, carry an enormous cost, estimated at upwards of 21 billion dollars per year. Hydroxyapatite (HAP) bio-ceramic has been widely used in clinic as a bone graft substitute material due to its biocompatibility and the similarity of its structure and composition to bone mineral. However, its applications are limited due to its lack of strength and toughness. Researchers have attempted to overcome these issues by combining HAP bio-ceramics into resorbable polymers to improve their mechanical properties. However, poor bonding between the HAP and the polymer caused separation at the polymer-filler interface. To overcome this, short chains of polymers were grafted directly from the hydroxyl groups on the surface of nanocrystalline HAP. Collagens, being the most abundant proteins in the body, and having suitable properties such as biodegradability, bioabsorbability with low antigenicity, high affinity to water, and the ability to interact with cells through integrin recognition, makes them a very promising candidate for the modification of the polymer surface. In this study, a novel method of synthesizing nano-hydroxyapatite (nHAP)-g-poly(lactide-co-glycolide)-g-collagen polymer was introduced. The synthesis process was carried out in several steps. First, poly (lactide-co-glycolide) (PLGA) polymer was directly grafted onto the hydroxyl group of the surface of n-HAP particles by ring-opening polymerization, and subsequently coupled with succinic anhydride. In order to activate the co-polymer for collagen attachment, the carboxyl end group obtained from succinic anhydride was reacted with N-hydroxysuccinimide (NHS) in the presence of dicyclohexylcarbodiimide (DCC) as the cross-linking agent. Finally, the activated co-polymer was attached to calf skin collagen type I, in hydrochloric acid/phosphate buffer solution and the precipitated co-polymer with attached collagen was isolated. The synthesis was monitored by 1H NMR and FTIR spectroscopies and the products after each step were characterized by thermal analysis (TGA and DSC). These composite materials will be tested as potential scaffolds for tissue engineering applications.

Recovery and physicochemical properties of smooth hound (mustelus mustelus) skin gelatin

Gelatin was extracted from the skin of smooth hound after pre-treatment with acetic and citric acids. The addition of smooth hound crud acid protease (SHCAP) at a level of 15 Units/g alkaline treated skin resulted in an increase yields of gelatin. The hydroxyproline yields of gelatins extracted for 24 h with acetic acid and with SHCAP were 17.34% and 56.82%, respectively. While the serine content recorded for the smooth hound skin gelatin (SHSG) extracted with SHCAP was higher than that of halal bovine gelatin (HBG) (36 versus 29 residues per 1000 residues), hydroxyproline and proline (202 residues per 1000 residues) contents were slightly lower (219 residues per 1000 residues). The gel strength of the gelatin gel from SHSG (211 g) was lower than that of HBG (259 g) (p < 0.05). Compared to HBG (p < 0.05), SHSG was noted to exhibit lower emulsifying, foaming, and fat-binding properties but similar emulsifying stability. SDS-PAGE revealed that SHSG showed high band intensity for the major protein components, especially α- and β-components, which was comparable to that of standard calf skin collagen type I. In conclusion gelatin extracted from smooth hound skin has good quality and can be used in the food industries.

Caprine (Goat) Collagen: A Potential Biomaterial for Skin Tissue Engineering

Collagens presently used in tissue engineering are primarily of bovine or porcine origin. However, a risk of a spongiform encephalopathy epidemic has limited the use of collagen from these sources. Keeping the aforementioned perspective in mind, we explored the possibility of using domestic goat available in the subcontinent as a potential source of collagen for tissue-engineering application. This article delineates the isolation, physico-chemical characterization, biocompatibility study and wound healing application of acid soluble caprine (goat) tendon collagen (GTC). Physico-chemical characterization of 1% acetic acid extracted GTC was done by SDS-PAGE, amino-acid composition analysis, FT-IR and CD spectroscopy. Results revealed that GTC was comprised of type-I collagen. Biocompatibility study showed that GTC augmented cell adhesion, cell cycle progression and proliferation. Immuno-cytochemical analysis in conjugation with traction force microscopy further confirmed a superior focal adhesion complex mediated cell–substrate interaction in GTC. Finally, in vivo study in mice model revealed that GTC has low immunogenicity and it augments healing process significantly. Throughout the study, calf skin collagen (CSC) was used as standard for comparative evaluation. In conclusion, it can be said that GTC may find its application as biomaterial in skin tissue engineering.

Chemical composition and characteristics of skin gelatin from grey triggerfish (Balistes capriscus)

Gelatin was extracted from the skin of grey triggerfish (Balistes capriscus) by the acid extraction process with a yield of 5.67 g/100 g skin sample on the basis of wet weight. The chemical composition and functional properties of gelatin were investigated. The gelatin had high protein (89.94 g/100 g) but low fat (0.28 g/100 g) contents. Differences in the amino acid composition between grey triggerfish skin gelatin (GSG) and halal bovine gelatin (HBG) were observed. GSG contained a lower number of imino acids (hydroxyproline and proline) (176 residues per 1000 residues) than HBG (219 residues per 1000 residues), whereas the content of serine was higher (40 versus 29 residues per 1000 residues, respectively). The gel strength of the GSG (168.3 g) was lower than that of HBG (259 g) (p < 0.05) possibly due to lower hydroxyproline content. Grey triggerfish skin gelatin exhibited a slightly lower emulsifying activity and water-holding capacity but greater emulsifying and foam stability, foam formation ability and fat-binding capacity than the halal bovine gelatin (p < 0.05). SDS-PAGE of GSG showed high band intensity for the major protein components, especially, α- and β-components and a similar molecular weight distribution to that of standard calf skin collagen type I.

Processing Optimization and Physicochemical Characteristics of Collagen from Scales of Yellowfin Tuna (Thunnus albacares)

This study was conducted to investigate the optimal conditions of collagen extraction from scales of yellowfin tuna (Thunnus albacares) using surface response methodology. Four independent variables of NaOH concentration and pretreatment fime in alkali pretreatment and enzyme concentration and treatment time in enzyme hydrolysis were used to predict a model equation for the collagen yield. The determinant coefficient (<TEX>$R^2$</TEX>) for the equation was 0.906. The values of the independent variables for the maximum yield were 0.32 N NaOH, 16.38 h alkali pretreatment time, 0.18% enzyme concentration, and 31.02 h enzyme treatment time. In the physicochemical properties of tuna scale collagen, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of tuna scale collagen showed the same migration distances as that of calf skin collagen. The amide A, I, II, and III regions of tuna scale collagen in Fourier transform infrared measurements were shown in the peaks of 3,414 <TEX>$cm^{-1}$</TEX>, 1,645 <TEX>$cm^{-1}$</TEX>, 1,553 <TEX>$cm^{-1}$</TEX>, and 1,247 <TEX>$cm^{-1}$</TEX>, respectively. The amount of imino acids in tuna scale collagen was 18.97% and the collagen denaturation temperature was <TEX>$33^{\circ}C$</TEX>. The collagen solubility as a function of NaCl concentration decreased to 4% NaCl (w/v) and the collagen solubility as a function of pH was high at pH 2-4 and sharply decreased from pH 4 to pH 7. Viscosity of the collagen solution decreased continuously until <TEX>$30^{\circ}C$</TEX> and this decreasing rate slowed in the temperature range of <TEX>$35-50^{\circ}C$</TEX>.

Isolation and characterisation of collagen extracted from the skin of striped catfish ( Pangasianodon hypophthalmus)

Acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from the skin of striped catfish ( Pangasianodon hypophthalmus) were isolated and characterised. The yields of ASC and PSC were 5.1% and 7.7%, based on the wet weight of skin, respectively, with the accumulated yield of 12.8%. Both ASC and PSC comprising two different α-chains (α1 and α2) were characterised as type I and contained imino acid of 206 and 211 imino acid residues/1000 residues, respectively. Peptide maps of ASC and PSC hydrolysed by either lysyl endopeptidase or V8 protease were slightly different and totally differed from those of type I calf skin collagen, suggesting some differences in amino acid sequences and collagen structure. Fourier transform infrared (FTIR) spectra of both ASC and PSC were almost similar and pepsin hydrolysis had no marked effect on the triple-helical structure of collagen. Both ASC and PSC had the highest solubility at acidic pH. A loss in solubility was observed at a pH greater than 4 or when NaCl concentration was higher than 2% (w/v). T max of ASC and PSC were 39.3 and 39.6 °C, respectively, and shifted to a lower temperature when rehydrated with 0.05 M acetic acid. Zeta potential studies indicated that ASC and PSC exhibited a net zero charge at pH 4.72 and 5.43, respectively. Thus, ASC and PSC were slightly different in terms of composition and structure, leading to somewhat different properties.

Compositional and physicochemical characteristics of acid solubilized collagen extracted from the skin of unicorn leatherjacket (Aluterus monoceros)

Abstract Acid solubilized collagen (ASC) was extracted from the skin of unicorn leatherjacket ( Aluterus monoceros ) using 0.5 M acetic acid, followed by precipitation with 2.6 M NaCl. ASC with the yield of 4.19% (wet weight basis) was identified as type I collagen, which was composed of two α 1 chains and one α 2 chain. Different peptide maps were observed between ASC hydrolyzed by V8 protease and lysyl endopeptidase. The maps were also different from those of type I collagen from calf skin, suggesting the differences in amino acid sequences between both collagens. Glycine was the most predominant amino acid. ASC contained the relatively higher content of alanine, but lower contents of proline and hydroxyproline, compared with calf skin collagen. FTIR analysis showed that ASC was in triple helix structure. T max of ASC dispersed in 0.05 M acetic acid and deionized water were 27.7 and 35.8 °C, respectively. Relative viscosity of 0.03% (w/v) ASC dissolved in 0.1 M acetic acid decreased continuously as the temperature increased from 4 to 52 °C, indicating thermal destabilization or denaturation of ASC molecules. ASC had the solubility greater than 90% in very acidic pH range (pH 1–4) and the solubility decreased continuously with increasing NaCl concentrations (0–6%). Net charge of ASC and calf skin collagen became zero at pHs of 5.58 and 5.68, respectively as determined by zeta potential titration. Therefore, skin of unicorn leatherjacket can be used as an alternative collagenous source.

Viscoelastic adlayers of collagen and lysozyme studied using quartz crystal microbalance with dissipation monitoring

In this study the effects of molecular structure of proteins on their adsorption behaviour and viscoelasticity are investigated using a QCM-D method. The adsorption measurements show that spherical lysozyme is rapidly adsorbed on the gold surface as a stiff monolayer, as indicated by a sharp drop in the oscillation frequency (Deltaf) of the sensor, and by a very small increase in the energy dissipation of the adlayer (DeltaD). Fibrous calfskin collagen (CSC) is, however, adsorbed on the same surface rather slowly in two steps to form a thick and soft multilayer (large Deltaf and DeltaD) at pH 3 in salt-free conditions. The two-step adsorption is not observed for stiffly aggregated CSC. This study clearly demonstrates that the polymer structure strongly affects not only how adsorption develops but also the viscoelastic properties of the adlayer.