DOCSLIB.ORG

Structures of Α-Keratin, Silk Fibrin and Collagen

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Structures of Α-Keratin, Silk Fibrin and Collagen Paper 4. Biomolecules and their interactions MODULE 6: Structures of -keratin, silk fibrin and collagen OBJECTIVES To learn about the structure and assembly of fibrous proteins. To learn structural details of α-keratin, silk fibrin and collagen. Introduction Fibrous proteins are also known as Scleroproteins. These form one branch of the three main types of the proteins present in nature. Many super families of proteins, including keratin and collagen fall under this class of proteins. Fibrous proteins particularly form long filaments, generally shaped like rods and wires. They are typically water-insoluble and inert proteins. They serve the cell as structural or storage proteins. Some of the functions include formation of connective tissues, muscle fiber etc. Due to the hydrophobic side chains that protrude from the surface of the molecule, fibrous proteins form aggregates. When compared to globular proteins, scleroproteins are resistant to denaturation. Fibrous proteins generally contain few amino acids that are often present as repeat sequences. They can form unusual secondary structures, for example: collagen helix. Keratin helix on the other hand displays cys-cys disulphide cross-linking between chains. Fibrous proteins are usually divided into three different groups • Coiled-coil -helices present in keratin and myosin • The triple helix in collagen • Beta-sheets in amyloid fibers and silks Coiled alpha helices can be seen in wool fibers giving elasticity and flexibility to it, whereas collagen fibers are relatively rigid and strong. Beta-sheet fibers are both strong and flexible. A classic example to quote would be that of spider web, some of which are even stronger than the same dimensional steel and highly flexible at the same time. Fibrous beta-sheet structures can be seen in various diseases like Alzheimers and prion disease as a result of protein misfolding, where the protein forms aggregate like structures, which are resistant to protease digestion. α-KERATIN Keratin is a fibrous structural protein that protects epithelial cells from potentially lethal damage or stress. Hence, it makes up the outer layer of the human skin. Keratin is also the key component of nails and hair. Tongue and the hard palate get the necessary strength for food mastication due to presence of keratin. Keratin monomers assemble in to bundles to form intermediate filaments that are tough and strong. These filaments make up the most of hard tissues found in reptiles, birds, amphibians, and also mammals. In general keratin filaments are abundant in keratinocytes and they are also found in epithelial cells. α-keratins are found in hair, hoofs, claws and horns of mammals, whereas β-keratins can be seen in nails and scales of reptiles and feathers, beaks and claws of birds. β-keratins are primarily composed of beta sheets and α-keratins mostly contain – helices. Hanukoglu and Fuchs determined the first sequences of keratins revealing two distinct but homologous keratin families namely Type I and Type II. From the sequence, it was proposed the presence of central 310 amino acids as 4 helices separated by 3 beta turn linker regions. Keratins or cytokeratins form type III and IV intermediate filaments that are found in chordates only. Keratin monomers left-handedly supercoiled in order to form a very stable super helical or coil- coiled structure. Along the length of the filament there are hydrophobic interactions between the non-polar amino acids and thus maintains the coiled-coil structure. For the structural details of coil-coiled structures, see the module super-secondary structures in module 9. Permanent rigidity is achieved by thermally stable cross-linking between cysteine residues present in the keratin filaments. This extensive disulphide bonding makes keratin insoluble. Keratins in hair are more flexible Monomer of Keratin molecule has about 310 central amino than those present in nails and acids, flanked by two globular domains. These individual hoofs due to presence of less molecules become dimer as coiled-coils. These dimers inter-chain disulphide bonds in assemble to form tetramer and octamer. The bundle of eight the former. Hair is composed of chains forms a intermediate filament or protofilamet. dead cells, each cell packed with (Figure adopted from Wikipedia) keratin macrofibrils. α-keratins are α- helically coiled single protein strands that contain regularly arranged intra-chain hydrogen bonds. Keratin monomers form long intermediate filaments beginning with the dimerisation, continue to oligomerise till the octamers are available for end- to-end joining to yield a long filamentous form. This can be viewed in the accompanying slides. By the process of cornification, stratified squamous epithelial cells form the skin barrier. Cells undergo programmed cell death and become fully keratinized. Clinical manifestations Since keratin is the building block of hair and nails, its disorders lead to significant deterioration in the mechanical integrity of these tissues. The disease and disorders could be a result of either gene mutations. Some of the disorders are: Monilethrix (also referred to as beaded hair) is a rare autosomal dominant hair disease that results in short, fragile, broken hair. Epidermolytic hyperkeratosis, (also known as Bullous congenital) is a rare skin disease affecting around 1 in 250,000 people. It is caused due to mutation in Keratin 1 gene. Large cell lung carcinoma with rhabdoid phenotype is a rare histological form of lung cancer, occurring mainly due to missense mutation in cytokeratin-8 gene. Keratin is also helpful in elucidating the epithelial origin of anaplastic cancers. Keratin, if ingested is highly resistant to digestive acids present in the gut. This could be the result of trichophagia, is the compulsive eating of hair. In some people trichophagia could also lead to a potentially fatal Rapunzel syndrome in humans, where small or large bowel obstruction by hair. COLLAGEN It is the main structural protein present in the extracellular matrix of many connective tissues, thus making it the most abundant protein in animal bodies. It is commonly found in tendons, ligaments and skin as elongated fibrils. Many other areas in the body also contain abundant amounts of keratin like corneas, bones, cartilage etc. Collagen fibers in bones are arranged at an angle to each other to give strength from all directions. Collagen constitutes one to two percent of muscle tissue, and accounts for 6% of the weight of strong, tendinous muscles. The fibroblast is the most common cell that creates collagen. The food industry puts collagen to its use in an irreversibly hydrolysed form of gelatin. In the field of medicine, collagen is used for treatment of skin and bone complications. Tensile strength of collagen results due to (a) The triple helix secondary structure (b) The assembly of tropocollagen subunits into a fibre (c) Chemical cross linking to strengthen the fibre (d) Collagen is formed from tropocollagen subunits. (e) The triple helix in tropocollagen is highly extended and strong. The amino acid residues present in collagen are different from the others found in rest of the proteins like hydroxyproline. The common motifs found in collagen are glycine-proline-X and glycine-X-hydroxyproline (X could be any amino acid other than glycine, proline or hydroxylproline). This shows presence of unusually high proline content nearly 17% of collagen. Another atypical amino acid that is seen is hydroxylysine. Types of collagen: Collagen is classified in to many groups on the basis how their structures are formed. Variations in the amino acid sequences of protein chains (generally called as chains) in collagen lead to slightly different properties, but they generally have same size. Fibrillar (Type I, II, III, V, XI) Non-fibrillar (Type IX, XII, XIV, XVI, XIX, VIII, X, IV, XV, XVIII, XIII, XVII, VI, VII) Collagen formation Collagen proteins longer precursors about 1000 amino acids, called pro-collagens with globular extensions about 200 amino acids at both ends, that contain signal sequences. They are transported to rough endoplasmic reticulum, where they are hydroxylated and then assembled into triple helix. Then the signal peptides are cleaved off releasing procollagen. Procollagen peptidase processes procollagen and forms tropocollagen. Three polypeptide strands, each has the conformation of a left-handed helix (not be confused with the right-handed alpha helix) to form collagen fiber. These three left- handed helices are twisted together into a right-handed triple helix or "super helix", a cooperative quaternary structure stabilized by many hydrogen bonds. Each collagen fiber has several micrometers long and 50 to Structure of Collagen with (Gly-Pro- 200 nanometers in diameter. The extended left hand Hyp)3 as sequence. (The figure is helix has 3.3 residues / turn with rise per each turn of adopted from Bhattacharjee and Bansal, 9.6 Å; rise per each amino acid is 2.9 Å. The triple IUBMB life, 2005.) helix has a repeat axis of 100 Å. Triple helical structure of collagen has one inter-chain hydrogen bond per tripeptide. In collagen triple helix H-bonds form between separate chains. In alpha-helix H-bonds are formed within the same chain. In this triple helix, every 3rd amino acid is close to the central axis, where there is no space and only Glycine can accommodate there. Any other residue deforms the triple helix. Hydrogen bonds are formed between NH groups of Glycine with CO groups of Proline of different chains. The adjoining slides depict the structural representation of collagen molecule. Hydroxy Pro or Pro containing triple helix of collagen structures are almost same. The combination of these amino acids (Gly-Pro-hydroxy Pro) prefers this conformation. In the triple helix structure hydroxyl Pro is always comes on the surface of the structure. Water mediated hydrogen bonds between inter and intra chain triple helices will differ and thus stability of triple helices must be different. There are different post-translation modifications and cross links in collagen which includes formation of hydroxyproline and hydroxylysine.
Load more

Recommended publications
  • Collagen and Elastin Fibres
    J Clin Pathol: first published as 10.1136/jcp.s3-12.1.49 on 1 January 1978. Downloaded from J. clin. Path., 31, Suppl. (Roy. Coll. Path.), 12, 49-58 Collagen and elastin fibres A. J. BAILEY From the Agricultural Research Council, Meat Research Institute, Langford, Bristol Although an understanding of the intracellular native collagen was generated from type I pro- biosynthesis of both collagen and elastin is of collagen. Whether this means that the two pro- considerable importance it is the subsequent extra- collagens are converted by different enzyme systems cellular changes involving fibrogenesis and cross- and the type III enzyme was deficient in these linking that ensure that these proteins ultimately fibroblast cultures, or that the processing of pro become the major supporting tissues of the body. type III is extremely slow, is not known. The latter This paper summarises the formation and stability proposal is consistent with the higher proportion of collagen and elastin fibres. of soluble pro type III extractable from tissue (Lenaers and Lapiere, 1975; Timpl et al., 1975). Collagen Basement membrane collagens, on the other hand, do not form fibres and this property may be The non-helical regions at the ends of the triple due to the retention of the non-helical extension helix of procollagen probably provide a number of peptides (Kefalides, 1973). In-vivo biosynthetic different intracellular functions-that is, initiating studies showing the absence of any extension peptide rapid formation of the triple helix; inhibiting intra- removal support this (Minor et al., 1976), but other cellular fibrillogenesis; and facilitating transmem- workers have reported that there is some cleavage brane movement.
    [Show full text]
  • Collagen and Creatine
    COLLAGEN AND CREATINE : PROTEIN AND NONPROTEIN NITROGENOUS COMPOUNDS Color index: . Important . Extra explanation “ THERE IS NO ELEVATOR TO SUCCESS. YOU HAVE TO TAKE THE STAIRS ” 435 Biochemistry Team • Amino acid structure. • Proteins. • Level of protein structure. RECALL: 435 Biochemistry Team Amino acid structure 1- hydrogen atom *H* ( which is distictive for each amino 2- side chain *R* acid and gives the amino acid a unique set of characteristic ) - Carboxylic acid group *COOH* 3- two functional groups - Primary amino acid group *NH2* ( except for proline which has a secondary amino acid) .The amino acid with a free amino Group at the end called “N-Terminus” . Alpha carbon that is attached to: to: thatattachedAlpha carbon is .The amino acid with a free carboxylic group At the end called “ C-Terminus” Proteins Proteins structure : - Building blocks , made of small molecules unit called amino acid which attached together in long chain by a peptide bond . Level of protein structure Tertiary Quaternary Primary secondary Single amino acids Region stabilized by Three–dimensional attached by hydrogen bond between Association of covalent bonds atoms of the polypeptide (3D) shape of called peptide backbone. entire polypeptide multi polypeptides chain including forming a bonds to form a Examples : linear sequence of side chain (R functional protein. amino acids. Alpha helix group ) Beta sheet 435 Biochemistry Team Level of protein structure 435 Biochemistry Team Secondary structure Alpha helix: - It is right-handed spiral , which side chain extend outward. - it is stabilized by hydrogen bond , which is formed between the peptide bond carbonyl oxygen and amide hydrogen. - each turn contains 3.6 amino acids.
    [Show full text]
  • The Close-Packed Triple Helix As a Possible New Structural Motif for Collagen
    The close-packed triple helix as a possible new structural motif for collagen Jakob Bohr∗ and Kasper Olseny Department of Physics, Technical University of Denmark Building 307 Fysikvej, DK-2800 Lyngby, Denmark Abstract The one-dimensional problem of selecting the triple helix with the highest volume fraction is solved and hence the condition for a helix to be close-packed is obtained. The close-packed triple helix is ◦ shown to have a pitch angle of vCP = 43:3 . Contrary to the conventional notion, we suggest that close packing form the underlying principle behind the structure of collagen, and the implications of this suggestion are considered. Further, it is shown that the unique zero-twist structure with no strain- twist coupling is practically identical to the close-packed triple helix. Some of the difficulties for the current understanding of the structure of collagen are reviewed: The ambiguity in assigning crystal structures for collagen-like peptides, and the failure to satisfactorily calculate circular dichroism spectra. Further, the proposed new geometrical structure for collagen is better packed than both the 10=3 and the 7=2 structure. A feature of the suggested collagen structure is the existence of a central channel with negatively charged walls. We find support for this structural feature in some of the early x-ray diffraction data of collagen. The central channel of the structure suggests the possibility of a one-dimensional proton lattice. This geometry can explain the observed magic angle effect seen in NMR studies of collagen. The central channel also offers the possibility of ion transport and may cast new light on various biological and physical phenomena, including biomineralization.
    [Show full text]
  • Evaluation of Elastin/Collagen Content in Human Dermis In-Vivo by Multiphoton Tomography—Variation with Depth and Correlation with Aging
    Cosmetics 2014, 1, 211-221; doi:10.3390/cosmetics1030211 OPEN ACCESS cosmetics ISSN 2079-9284 www.mdpi.com/journal/cosmetics Article Evaluation of Elastin/Collagen Content in Human Dermis in-Vivo by Multiphoton Tomography—Variation with Depth and Correlation with Aging Jean-Christophe Pittet 1,*, Olga Freis 2,†, Marie-Danielle Vazquez-Duchêne 2,†, Gilles Périé 2,† and Gilles Pauly 2,† 1 Orion Concept, 100 Rue de Suède, 37100 Tours, France 2 BASF Beauty Care Solutions France SAS, 3 Rue de Seichamps, CS 71040 Pulnoy, 54272 Essey-lès-Nancy Cedex, France; E-Mails: [email protected] (O.F.); [email protected] (M.-D.V.-D.); [email protected] (G.Pé.); [email protected] (G.Pa.) † These authors contributed equally to this work. * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +33-247-052-316; Fax: +33-610-786-695. Received: 14 March 2014; in revised form: 31 July 2014 / Accepted: 1 August 2014 / Published: 20 August 2014 Abstract: The aim of this study was to evaluate the influence of the depth of the dermis on the measured collagen and elastin levels and to establish the correlation between the amount of these two extracellular matrix (ECM) components and age. Multiphoton Microscopy (MPM) that measures the autofluorescence (AF) and second harmonic generation (SHG) was used to quantify the levels of elastin and collagen and to determine the SAAID (SHG-to-AF Aging Index of Dermis) at two different skin depths. A 50 MHz ultrasound scanner was used for the calculation of the Sub Epidermal Non Echogenic Band (SENEB).
    [Show full text]
  • Non-Linearity of the Collagen Triple Helix in Solution and Implications for Collagen Function
    Biochemical Journal (2017) 474 2203–2217 DOI: 10.1042/BCJ20170217 Research Article Non-linearity of the collagen triple helix in solution and implications for collagen function Kenneth T. Walker1, Ruodan Nan1, David W. Wright1, Jayesh Gor1, Anthony C. Bishop2, George I. Makhatadze2, Barbara Brodsky3 and Stephen J. Perkins1 1Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, U.K.; 2Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180-3590, U.S.A.; and 3 Department of Biomedical Engineering, Science and Technology Center, Tufts University, 4 Colby Street, Medford, MA 02155, U.S.A. Correspondence: S. J. Perkins ([email protected]) or B. Brodsky ([email protected]) Collagen adopts a characteristic supercoiled triple helical conformation which requires a repeating (Xaa-Yaa-Gly)n sequence. Despite the abundance of collagen, a combined experimental and atomistic modelling approach has not so far quantitated the degree of flexibility seen experimentally in the solution structures of collagen triple helices. To address this question, we report an experimental study on the flexibility of varying lengths of collagen triple helical peptides, composed of six, eight, ten and twelve repeats of the most stable Pro-Hyp-Gly (POG) units. In addition, one unblocked peptide, (POG)10unblocked, was compared with the blocked (POG)10 as a control for the significance of end effects. Complementary analytical ultracentrifugation and synchrotron small angle X-ray scattering data showed that the conformations of the longer triple helical peptides were not well explained by a linear structure derived from crystallography.
    [Show full text]
  • The Recognition of Collagen and Triple-Helical Toolkit Peptides By
    THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 289, NO. 35, pp. 24091–24101, August 29, 2014 Author’s Choice © 2014 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A. The Recognition of Collagen and Triple-helical Toolkit Peptides by MMP-13 SEQUENCE SPECIFICITY FOR BINDING AND CLEAVAGE* Received for publication, May 30, 2014, and in revised form, July 2, 2014 Published, JBC Papers in Press, July 9, 2014, DOI 10.1074/jbc.M114.583443 Joanna-Marie Howes‡, Dominique Bihan‡, David A. Slatter‡, Samir W. Hamaia‡, Len C. Packman‡, Vera Knauper§, Robert Visse¶, and Richard W. Farndale‡1 From the ‡Department of Biochemistry, University of Cambridge, Downing Site, Cambridge CB2 1QW, United Kingdom, the §Cardiff University Dental School, Dental Drive, Cardiff CF14 4XY, United Kingdom, and the ¶Kennedy Institute of Rheumatology, Hammersmith, London W6 8LH, United Kingdom Background: MMP-13 recognizes poorly-defined sequences in collagens. Results: MMP-13 binds key residues in the canonical cleavage site and another site near the collagen N terminus. Conclusion: MMP-1 and MMP-13 differ in their recognition and cleavage of collagen, which is regulated primarily through the Downloaded from Hpx domain of MMP-13. Significance: Our data explain the preference of MMP-13 for collagen II. Remodeling of collagen by matrix metalloproteinases (MMPs) is right-handed collagen superhelix, which endows the molecule crucial to tissue homeostasis and repair. MMP-13 is a collagen- with resistance to degradation by most proteases. The fibrillar http://www.jbc.org/ ase with a substrate preference for collagen II over collagens I collagens I, II, and III contain a conserved triple-helical COL and III.
    [Show full text]
  • Blood Vitronectin Is a Major Activator of LIF and IL-6 in the Brain Through Integrin–FAK and Upar Signaling Matthew P
    © 2018. Published by The Company of Biologists Ltd | Journal of Cell Science (2018) 131, jcs202580. doi:10.1242/jcs.202580 RESEARCH ARTICLE Blood vitronectin is a major activator of LIF and IL-6 in the brain through integrin–FAK and uPAR signaling Matthew P. Keasey1, Cuihong Jia1, Lylyan F. Pimentel1,2, Richard R. Sante1, Chiharu Lovins1 and Theo Hagg1,* ABSTRACT Microglia and astrocytes express the VTN receptors αvβ3 and α β We defined how blood-derived vitronectin (VTN) rapidly and potently v 5 integrin (Herrera-Molina et al., 2012; Kang et al., 2008; activates leukemia inhibitory factor (LIF) and pro-inflammatory Milner, 2009; Welser-Alves et al., 2011). Microglia and astrocytes, interleukin 6 (IL-6) in vitro and after vascular injury in the brain. as well as endothelial cells, are major producers of pro- α in vitro Treatment with VTN (but not fibrinogen, fibronectin, laminin-111 or inflammatory cytokines, such as IL-6 and TNF , and collagen-I) substantially increased LIF and IL-6 within 4 h in after traumatic or ischemic injury to the brain (Banner et al., 1997; C6-astroglioma cells, while VTN−/− mouse plasma was less effective Erta et al., 2012; Lau and Yu, 2001) or upon self-induction by IL-6 than that from wild-type mice. LIF and IL-6 were induced by (Van Wagoner and Benveniste, 1999). IL-6 is a major regulator of a intracerebral injection of recombinant human (rh)VTN in mice, but variety of inflammatory disorders and a target for therapies (Hunter induction seen upon intracerebral hemorrhage was less in VTN−/− and Jones, 2015).
    [Show full text]
  • Helix Stability of Oligoglycine, Oligoalanine, and Oligoalanine
    proteins STRUCTURE O FUNCTION O BIOINFORMATICS Helix stability of oligoglycine, oligoalanine, and oligo-b-alanine dodecamers reflected by hydrogen-bond persistence Chengyu Liu,1 Jay W. Ponder,1 and Garland R. Marshall2* 1 Department of Chemistry, Washington University, St. Louis, Missouri 63130 2 Department of Biochemistry and Molecular Biophysics, Washington University, St. Louis, Missouri 63130 ABSTRACT Helices are important structural/recognition elements in proteins and peptides. Stability and conformational differences between helices composed of a- and b-amino acids as scaffolds for mimicry of helix recognition has become a theme in medicinal chemistry. Furthermore, helices formed by b-amino acids are experimentally more stable than those formed by a-amino acids. This is paradoxical because the larger sizes of the hydrogen-bonding rings required by the extra methylene groups should lead to entropic destabilization. In this study, molecular dynamics simulations using the second-generation force field, AMOEBA (Ponder, J.W., et al., Current status of the AMOEBA polarizable force field. J Phys Chem B, 2010. 114(8): p. 2549–64.) explored the stability and hydrogen-bonding patterns of capped oligo-b-alanine, oligoalanine, and oligo- glycine dodecamers in water. The MD simulations showed that oligo-b-alanine has strong acceptor12 hydrogen bonds, but surprisingly did not contain a large content of 312-helical structures, possibly due to the sparse distribution of the 312-helical structure and other structures with acceptor12 hydrogen bonds. On the other hand, despite its backbone flexibility, the b- alanine dodecamer had more stable and persistent <3.0 A˚ hydrogen bonds. Its structure was dominated more by multicen- tered hydrogen bonds than either oligoglycine or oligoalanine helices.
    [Show full text]
  • With Caviar, Keratin & Collagen
    WITH CAVIAR, KERATIN & COLLAGEN Professional treatments for colour, bleaching, care and maintenance with CAVIAR, KERATIN and COLLAGEN Professional styling products with CAVIAR, KERATIN and COLLAGEN Technical professional products with CAVIAR, KERATIN and COLLAGEN 2 Professional products by Very high technology professional products to colour, treat and protect hair from the continuous chemical and environmental stress caused on a daily basis. Formulas based on: Caviar Keratin Collagen 3 WITH CAVIAR, KERATIN & COLLAGEN Colouring permanentCream professional ammonia PPD • Respects the hair structure thanks to an exposure free free time of 12 minutes • Non-progressive • Ammonia free • Paraphenylenediamine free • Unleashes all the EFFICANCY of its active principles and maximum COLOURING POWER Mix 1 : 1 4 WITH CAVIAR, KERATIN & COLLAGEN 1. Respect for scalp and hair thanks to a shorter processing time 2. Maximum grey hair coverage 3. Lightens up to 4 tones 4. Ammonia free and Paraphenylenediamine free 5. Safe application even on customers with a sensitive scalp 6. Extreme colour brilliancy and uniformity 7. Very easy and practical to use 8. Long lasting reflections 9. High colour fastness 10. Great protection action 11. Effective restructuring action benefits 12. Maximum conditioning 5 WITH CAVIAR, KERATIN & COLLAGEN Benefits 1 2 3 Respect for scalp and hair thanks to a shorter processing Lightens up to Maximum grey hair 4 tones time coverage 6 WITH CAVIAR, KERATIN & COLLAGEN has been developed according Cosmetic colour pDT BASE Be Colour 12 Minute Dpe DIAMINOPHENOXYETHANOL to the rules of the “molar stoichiometry,” a technique creamy gel with RESORCINOL m-AMINOPHENOL of colouring clear and uncompromising. It is based on CAVIAR, a mathematical principle according to which the molar concentration of the dye base is equal to the molar KERATIN and concentration of the sum of the other colouring couplers.
    [Show full text]
  • Effect of Starch on Property of Silk Fibroin/Keratin Blend Films
    International Journal of GEOMATE, Dec., 2016, Vol. 11, Issue 28, pp.2870-2873 Special Issue on Science, Engineering and Environment, ISSN: 2186-2990, Japan EFFECT OF STARCH ON PROPERTY OF SILK FIBROIN/KERATIN BLEND FILMS Yaowalak Srisuwan, Ansaya Thonpho and Prasong Srihanam Faculty of Science, Mahasarakham University, Maha Sarakham 44150, Thailand ABSTRACT: This work was aimed to study the effect of starch on silk fibroin (SF)/keratin (K) blend films properties. The SF and K solutions were mixed with starch, homogeneously stirred and poured into polystyrene culture plates. The mixture solution was then dried in an oven at 40 °C for 3 days. The films were then investigated for their morphology, secondary structure and thermal properties by using scanning electron microscope (SEM), Fourier transform-infrared (FT-IR) spectrophotometer, Thermogravimetric analysis (TGA). The results found that each film had different patterns of surfaces depending on ratio used. The structure of almost films co-existed with random coil and α-helix structures which resulted to increase the flexibility and of film. The structure of the films changed to β-sheet after blending between SF and K according to H-bond formation and increased thermal stability of the films. This result indicated that starch helped to decrease the crystalline structure of the film which increased their flexibility. Keywords: Biopolymer, Morphology, Secondary structure, Thermal property 1. INTRODUCTION Silk fibroin (SF) solution was prepared by firstly boiling twice of B. mori cocoons in 0.5% (w/v) Silk is a natural fibrous protein produced from Na2CO3 solution at 90 °C for 30 min in each times, silkworm which had a unique characteristic.
    [Show full text]
  • What Is Collagen?
    What is Collagen? Collagen is the most abundant protein in the human body and is as diverse as it is multifunctional (1). It is found throughout the body in a variety of forms and functions making up 30 percent of your body tissue and 70 % of your skin tissue. Specifically, collagen is the protein in connective tissue that is in bone marrow, tendons, cartilage, ligaments, and linings of your body organs. It is often referred to as the glue of the body. (1) Hydrolyzed collagen means the protein has been broken down into individual amino acids which are easier for the body to absorb. Collagen serves to help repair tissue and also functions in various roles throughout the body. Collagen and the Body Locations of Collagen: What Does Collagen Do? Collagen has numerous structural properties but also plays a vital role in the repair of almost all the body’s tissues. Some diseases are directly linked to lacking this essential protein. Depending on which part of the body it is located, collagen serves different purposes. In skin: Found in the inner layer, this connective tissue gives the skin its structure and strength and also functions in the replacement of dead skin cells. A lack of collagen in the skin can contribute to a decrease in skin health leading to stretch marks, dark spots, and infections as well as affecting the skin’s ability to maintain moisture. In internal organs and blood vessels: In the lining of your organs like in the stomach, kidneys, blood vessels and spleen, collagen functions as a protective covering and a fibrous barrier.
    [Show full text]
  • Helix Capping'
    Prorein Science (1998), 721-38. Cambridge University Press. Printed in the USA. Copyright 0 1998 The Protein Society REVIEW Helix capping' RAJEEV AURORA AND GEORGE D. ROSE Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, Maryland 21205 (RECEIVED June12, 1997; ACCEPTEDJuly 9, 1997) Abstract Helix-capping motifs are specific patterns of hydrogen bonding and hydrophobic interactions found at or near the ends of helices in both proteins and peptides. In an a-helix, the first four >N- H groups and last four >C=O groups necessarily lack intrahelical hydrogen bonds. Instead, such groups are often capped by alternative hydrogen bond partners. This review enlarges our earlier hypothesis (Presta LG, Rose GD. 1988. Helix signals in proteins. Science 240:1632-1641) to include hydrophobic capping. A hydrophobic interaction that straddles the helix terminus is always associated with hydrogen-bonded capping. From a global survey among proteins of known structure, seven distinct capping motifs are identified-three at the helix N-terminus and four at the C-terminus. The consensus sequence patterns of these seven motifs, together with results from simple molecular modeling, are used to formulate useful rules of thumb for helix termination. Finally, we examine the role of helix capping as a bridge linking the conformation of secondary structure to supersecondary structure. Keywords: alpha helix; protein folding; protein secondary structure The a-helixis characterized by consecutive, main-chain, i + i - 4 apolar residues in the a-helix and its flanking turn. This hydro- hydrogen bonds between each amide hydrogen and a carbonyl phobic component of helix capping was unanticipated.
    [Show full text]