Resilin

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Beating of the maxillipeds of the crayfish Pacifastacus leniusculus captured at a frame rate of 1000 Hz
Pro-resilin
Identifiers
Organism Drosophila melanogaster
Symbolresilin
Alt. symbolsCG15920
UniProt Q9V7U0
Search for
Structures Swiss-model
Domains InterPro

Resilin is an elastomeric protein found in many insects and other arthropods. It provides soft rubber-elasticity to mechanically active organs and tissue; for example, it enables insects of many species to jump or pivot their wings efficiently. Resilin was first discovered by Torkel Weis-Fogh in locust wing-hinges.

Contents

Resilin is currently the most efficient elastic protein known (Elvin et al., 2005). The elastic efficiency of the resilin isolated from locust tendon has been reported to be 97% (only 3% of stored energy is lost as heat). It does not have any regular structure but its randomly coiled chains are crosslinked by di- and tri-tyrosine links at the right spacing to confer the elasticity needed to propel some jumping insects distances up to 38 times their length (as found in fleas). Resilin must last for the lifetime of adult insects and must therefore operate for hundreds of millions of extensions and contractions; its elastic efficiency ensures performance during the insect's lifetime. Resilin exhibits unusual elastomeric behavior only when swollen in polar solvents such as water.

In 2005, a recombinant form of the resilin protein of the fly Drosophila melanogaster was synthesized by expressing a part of the fly gene in the bacterium Escherichia coli . Active studies are investigating potential application of recombinant resilins in biomedical engineering and medicine.

Occurrence

After its discovery in elastic tendons in dragon flies and wing hinges in locusts, resilin has been found in many structures and organs in arthropods. [1] Resilin is often found as a composite with chitin in insect cuticle, where chitin serves as the structural component. Resilin provides elasticity and possibly other properties. It has been discovered in the salivary pump of assassin bugs ( Rhodnius prolixus ), tsetse flies, and honey bees, and in the resistance providing mechanism for the venom-dispensing pump of honey bee stingers. Resilin has also been found in the sound production organs of arthropods, such as cicadas and the moth family Pyralidae, where both high elasticity and high resilience of resilin play important roles due to the rapid stress-release cycles of sound-producing tymbals. Besides these structures, resilin exists most widely in the locomotion systems of arthropods. It was discovered in wing hinges to enable recovery from deformation of wing elements, and to dampen the aerodynamic forces felt by the wing; in ambulatory systems of cockroaches and flies to facilitate rapid joint deformation; in jumping mechanisms, resilin stores kinetic energy with great efficiency and releases it upon unloading. It is also abundant in the cuticle surrounding the abdomens of termites, ants, and bees, which expand and swell to a great extent during feeding and reproduction process. [1]

Composition of resilin

Amino acid constituents

Amino Acid Composition of resilin The Different Amino Acid Composition of Resilin.png
Amino Acid Composition of resilin

Amino acid composition in resilin was analyzed in 1961 by Bailey and Torkel Weis-Fogh when they observed samples of prealar arm and wing hinge ligaments of locusts. The result indicates that resilin lacks methionine, hydroxyproline, and cysteine constituents in its amino acid composition. [2]

Protein sequence

Resilin was identified to be a product of the Drosophila melanogaster gene CG15920 due to the similarities between amino acid compositions of resilin and the gene product. [3] The Drosophila melanogaster gene is composed of 4 exons, which encode for 4 functional segments in CG15920: signal peptide and 3 peptide encoded by exon 1, 2, and 3. [4] The signal peptide guides pro-resilin into extracellular space, where resilin proteins aggregate and cross link to form a network, and then is cut off from the peptides, so that nascent resilin becomes mature resilin. From the N-terminal, segment encoded by exon 1 contains 18 copies of a 15-residue repeating sequence (GGRPSDSYGAPGGGN); segment corresponding to exon 2 contains 62 amino acids of the chitin-binding Rebers-Riddiford (R-R) consensus sequence (Pfam PF00379); exon 3 encoded peptide is dominated by 11 copies of a 13-residual repeating sequence (GYSGGRPGGQDLG). While enriched glycine and proline in exon 1 and 3 introduce cyclic structures into the protein, tyrosine residuals are able to form di- and tri-tyrosine cross-links between proteins.

Secondary structure

The Mechanism of Action of resilin Mechanism of Action of Resilin.png
The Mechanism of Action of resilin

Resilin is a disordered protein; however its segments may take on secondary structures under different conditions. It is discovered that peptide sequence encoded by exon 1 exhibit an unstructured form and cannot be crystallized, which allows the peptide sequence segment to be very soft and highly flexible. Exon 3 encoded peptide takes on the unstructured form before loading, but transforms to an ordered beta-turn structure once stress is applied. Meanwhile, segment encoded by exon 2 serves as a chitin binding domain. [4] It is proposed that as stress is applied, or there is energy input, exon 1 encoded peptide responds immediately due to its high flexibility. Once this occurs, the energy is passed onto exon 3 encoded peptide, which transforms from the unstructured form to beta-turn structure to store energy. Once the stress or energy is removed, exon 3 encoded segment reverses the structural transformation and outputs the energy to exon 1 encoded segment. [4]

Another secondary structure exon 1 and exon 3 corresponding peptides may take on is the polyproline helix (PPII), indicated by the high occurrence of proline and glycine in these 2 segments. The PPII structure widely exists in elastomeric proteins, such as abductin, elastin, and titin. [5] It is believed to contribute in the self-assembling process and the elasticity of the protein. [4] The elastic mechanism of resilin is proposed to be entropy related. Under relaxed state, the peptide is folded, and possesses a large entropy, but once it is stretched out, the entropy decreases as the peptide unfold. The coexistence of PPII and beta-turn play an important role of increasing entropy as resilin returns to its disordered form. [6] The other function of PPII is to facilitate self-assembling process: it is found that the quasi-extended PPII is able to interact through an intermolecular reaction, and initiate the formation of fibrillar supramolecular structure. [6]

Hierarchical structure

While the secondary structures are determined by energy state and hydrogen bonds formed between amino acids, hierarchical structures are determined by the hydrophobicity of the peptide. Exon 1 encoded peptide is mainly hydrophilic, and is more extended when immersed in water. [7] In contrast, exon 3 encoded peptide contains both hydrophobic and hydrophilic blocks, suggesting the formation of micelles, where the hydrophobic block will cluster on the inside with the hydrophilic portion surrounding it. [7] Thus, a single complete resilin protein, when immersed in water, takes on the structure in which exon 1 encoded segment extends out from the micelle exon 3 encoded peptide forms. [7]

Once resilin is transferred to the outside of the cell, their exon 2 encoded peptides, the chitin binding segments, bind to chitin. [1] Meanwhile, di- or tri-tyrosine crosslinking is formed by oxidative coupling, mediated by peroxidase, between tyrosine residuals. [1] Like other elastomeric proteins, the degree of cross linking in resilin is low, which ensures the low stiffness and high resilience. Cross linked peptides encoded by exon 1 have a resilience greater than 93%, while that encoded by exon 3 has a resilience of 86%. In addition, natural resilin has a resilience of 92%, similar to that of exon 1, suggesting again that exon 1 may play a more important role in the elastic property of resilin. [4]

Tyrosine residues in resilin

Andersen, in 1996, discovered that the tyrosine residues are involved in chemically covalent cross-links in many forms such as dityrosine, trityrosine, and tetratyrosine. [8] Primarily, in resilin, tyrosine and dityrosine served as the chemical cross-links, in which R groups of Tyrosine and Dityrosine add to the backbone of the growing peptide chain. [1] Andersen came to this conclusion based on a study involving these two compounds in which he was able to rule out other forms of cross linking such as disulfide bridges, ester groups, and amide bonds. [1] Though the mechanism of cross-linking of Tyrosine is understood that occurs through radical initiation, the cross linking of resilin still remains a mystery. Cross linking of resilin occurs very quickly and this is possibly a result of temperature. At increasing temperature, the rate of cross linking of the residues increases and leads to a highly cross-linked resilin network. [1]

The amino acid composition of resilin indicates that proline and glycine has a relatively high presence in the amino acid composition of resilin. The presence of glycine and proline in the composition of resilin contributes greatly to the elasticity of resilin. [9] Resilin, however, has an absence of an alpha-helix leading to a randomly coiled structure and a disordered structure. [10] This is primarily due to the significantly high proline content in resilin. Proline is a bulky amino acid that has the ability to cause a kink the peptide chain and due to the sterically hindered side chains, it is not able to fit in the alpha-helices. However, the segments of resilin are able to take on secondary structure forms at different conditions.

Properties

Like other biomaterials, resilin is a hydrogel, meaning it is swollen with water. The water content of resilin at neutral pH is 50-60%, and the absence of this water will make a big difference on the material's property: while the hydrated resilin behaves like a rubber, the dehydrated resilin has the properties of a glassy polymer. [1] However, dehydrated resilin is able to return to its rubbery state if water is available. Water serves as a plasticizer in resilin network by increasing the amount of hydrogen bonds. [4] The high concentration of proline and glycine, polyproline helices, and hydrophilic portions all serves to increase water content in resilin protein network. The increase in hydrogen bonds lead to an increase in chain mobility, thus decreases glass transition temperature. The more water content is in resilin network, the less stiff and more resilient the material is. Dehydrated resilin behaves as a glass polymer with low stiffness, strain, and resilience, but a relatively high compressible modulus and glass transition temperature. [1]

Rubber like proteins, such as resilin and elastin, are characterized based on their high resilience, low stiffness, and large strain. [11] A high resilience indicate that a sufficient amount of energy input can be stored in the material, and released afterwards. An example of energy input is to stretch the material. Natural resilin (hydrated) has a resilience of 92%, which means it can store 92% of the energy input for release during unloading, indicating a very efficient energy transfer. In order for a better understanding the stiffness and strain of resilin, Hooke's Law should be taken into consideration. For linear springs, Hooke's Law states that the force required to deform the spring is directly proportional to the amount of deformation by a constant which is the characteristic of the spring. A material is viewed as elastic when it can be deformed to a large extend with a limited amount of force. Hydrated resilin has a tensile modulus of 640-2000 kPa, an unconfined compressive modulus of 600-700 kPa, and a strain to break of 300%. [4]

Table 1: Properties of Hydrated and Dehydrated Resilin
PropertiesHydrated ResilinDehydrated Resilin
Elastic Modulus588 kPa [1] -
Compressive Modulus600-700 kPa [4] 10,200 ± 2% kPa [4]
Tensile Modulus640-2000 kPa [4] -
Tensile Strength4MPa [4] -
Maximum Strain300% [4] -
Resilience92% [4] -
Tg°<37 °C [4] >180 °C [4]

Although there has been no actual data acquired for the fatigue lifetime of resilin, we can think about this intuitively. If we consider the case of honey bees, where they live for around 8 weeks during which they fly 8 hours a day, flapping wings at 720,000 cycles/h, they are likely to flap their wings more than 300 million times [9]. Since resilin functions over the entire lifetime of insects, its fatigue lifetime should be considerably large. However, in live insects, resilin molecular can be produced and replaced constantly, which introduces an error in our conclusion.

Recombinant resilin

Initial studies

Due to the remarkable rubber elasticity of resilin, scientists began exploring recombinant versions for a variety of material and medical applications. With the rise in DNA technologies, this field of research has seen a rapid increase in the synthesis of biosynthetic protein polymers that can be tuned to having certain mechanical properties. Thus, this field of research is rather promising and can provide new methods for treating diseases and disorders that affect the population. Recombinant resilin was first studied in 2005 when it was expressed in Escherichia coli from the first exon of the Drosophila Melanogaster's CG15920 gene. [12] During its study, pure resilin was synthesized into 20% protein-mass hydrogel and was cross-linked with ruthenium-catalyzed tyrosine in the presence of ultraviolet light. [12] This reaction yielded the product, recombinant resilin (rec1-Resilin). [12]

One of the most important aspects of successful rec1-Resilin synthesis is that its mechanical properties match that of the original resilin (native resilin). In the study indicated above, Scanning Probe Microscopy (SPM) and Atomic Force Microscopy (AFM) were used to investigate the mechanical properties of rec1-Resilin and native resilin. [1] The results of these tests revealed that the resilience of both recombinant and native resilin were relatively similar but can differ in its applications. [1] In this study, rec1-Resilin could be placed into a polymeric scaffold to mimic the extracellular matrix in order to generate a cell and tissue responses. Though this field of research is still ongoing, it has generated a wide amount of interest in the scientific community and is currently being investigated for a variety of biomedical applications in areas of tissue regeneration and repair.

Fluorescence of recombinant resilin

One unique property of rec1-Resilin is its ability to be identified due to autofluorescence. Fluorescence for resilin stems primarily from dityrosine, which are the result of crosslinks of tyrosine residues. When ultraviolet light irradiates a sample of rec1-Resilin at 315 nm to 409 nm emissions, the rec1-Resilin begins to show blue fluorescence. [12] An example of the blue fluorescence exhibited by the dityrosine residues in resilin is shown in the figure below of a flea.

CSIRO Image of a flea with detail showing the resilin pad CSIRO ScienceImage 1088 Image of a flea with detail showing the resilin pad.jpg
CSIRO Image of a flea with detail showing the resilin pad

Resilience

Another unique property of resilin is its high resilience. Recombinant resilin demonstrated excellent mechanical properties similar to that of pure resilin. Elvin et al. aimed to compare the resilience of rec1-Resilin to other rubbers, a scanning probe microscope of used. This study compared the resilience of rec1-Resilin to two different types of rubber: chlorobutyl rubber and polybutadiene rubber, both rubbers with high resilience properties. [12] This study concluded that rec1-Resilin was 92% resilient compared to chlorobutyl rubber at 56% and polybutadiene rubber at 80%, respectively. [12] With such high mechanical resilience, the properties of rec1-Resilin can be applied to other clinical applications within the field of Materials Engineering and Medicine. This study on recombinant resilin has led to several years of research on the use of resilin like proteins for several biomedical applications that retains the mechanical properties of resilin. The ongoing results of the studies involving recombinant resilin may lead to further research in which other unexplored mechanical properties and chemical structure of resilin may be investigated.

Clinical applications

Recombinant resilins have been studied for potential application in the fields of biomedical engineering and medicine. In particular, hydrogels composed of recombinant resilins have been utilized as tissue engineering scaffolds for mechanically-active tissues including cardiovascular, cartilage and vocal cord tissues. Early work has focused on optimizing the mechanical properties, chemistry and cytocompability of these materials, but some in vivo testing of resilin hydrogels has also been performed. [13] Researchers at the University of Delaware and Purdue University have developed methods for creating elastic hydrogels composed of resilin that were compatible with stem cells and displayed similar rubber elasticity to that of natural resilin. [14] [15] [16] [17] Semi-synthetic resilin-based hydrogels, which incorporate poly(ethylene glycols), have also been reported. [18]

See also

Related Research Articles

<span class="mw-page-title-main">Amino acid</span> Organic compounds containing amine and carboxylic groups

Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 appear in the genetic code of life.

<span class="mw-page-title-main">Biopolymer</span> Polymer produced by a living organism

Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, classified according to the monomers used and the structure of the biopolymer formed: polynucleotides, polypeptides, and polysaccharides. The Polynucleotides, RNA and DNA, are long polymers of nucleotides. Polypeptides include proteins and shorter polymers of amino acids; some major examples include collagen, actin, and fibrin. Polysaccharides are linear or branched chains of sugar carbohydrates; examples include starch, cellulose, and alginate. Other examples of biopolymers include natural rubbers, suberin and lignin, cutin and cutan, melanin, and polyhydroxyalkanoates (PHAs).

<span class="mw-page-title-main">Protein</span> Biomolecule consisting of chains of amino acid residues

Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity.

<span class="mw-page-title-main">Protein primary structure</span> Linear sequence of amino acids in a peptide or protein

Protein primary structure is the linear sequence of amino acids in a peptide or protein. By convention, the primary structure of a protein is reported starting from the amino-terminal (N) end to the carboxyl-terminal (C) end. Protein biosynthesis is most commonly performed by ribosomes in cells. Peptides can also be synthesized in the laboratory. Protein primary structures can be directly sequenced, or inferred from DNA sequences.

Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group -NH
2
but is rather a secondary amine. The secondary amine nitrogen is in the protonated form (NH2+) under biological conditions, while the carboxyl group is in the deprotonated −COO form. The "side chain" from the α carbon connects to the nitrogen forming a pyrrolidine loop, classifying it as a aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it from the non-essential amino acid L-glutamate. It is encoded by all the codons starting with CC (CCU, CCC, CCA, and CCG).

<span class="mw-page-title-main">Gel</span> Highly viscous liquid exhibiting a kind of semi-solid behavior

A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady state, although the liquid phase may still diffuse through this system. A gel has been defined phenomenologically as a soft, solid or solid-like material consisting of two or more components, one of which is a liquid, present in substantial quantity.

<span class="mw-page-title-main">Proteinogenic amino acid</span> Amino acid that is incorporated biosynthetically into proteins during translation

Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word "proteinogenic" means "protein creating". Throughout known life, there are 22 genetically encoded (proteinogenic) amino acids, 20 in the standard genetic code and an additional 2 that can be incorporated by special translation mechanisms.

<span class="mw-page-title-main">Elastin</span> Protein allowing tissue in the body to resume shape after stretching

Elastin is a protein that in humans is encoded by the ELN gene. Elastin is a key component of the extracellular matrix in gnathostomes. It is highly elastic and present in connective tissue allowing many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it is poked or pinched. Elastin is also an important load-bearing tissue in the bodies of vertebrates and used in places where mechanical energy is required to be stored.

<span class="mw-page-title-main">Elastomer</span> Polymer with rubber-like elastic properties

An elastomer is a polymer with viscoelasticity and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. The term, a portmanteau of elastic polymer, is often used interchangeably with rubber, although the latter is preferred when referring to vulcanisates. Each of the monomers which link to form the polymer is usually a compound of several elements among carbon, hydrogen, oxygen and silicon. Elastomers are amorphous polymers maintained above their glass transition temperature, so that considerable molecular reconformation is feasible without breaking of covalent bonds. At ambient temperatures, such rubbers are thus relatively compliant and deformable. Their primary uses are for seals, adhesives and molded flexible parts.

<span class="mw-page-title-main">Hydrogel</span> Soft water-rich polymer gel

A hydrogel is a biphasic material, a mixture of porous, permeable solids and at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. In hydrogels the porous permeable solid is a water insoluble three dimensional network of natural or synthetic polymers and a fluid, having absorbed a large amount of water or biological fluids. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature. The term 'hydrogel' was coined in 1894.

<span class="mw-page-title-main">Titin</span> Largest-known protein in human muscles

Titin is a protein that in humans is encoded by the TTN gene. Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring that is responsible for the passive elasticity of muscle. It comprises 244 individually folded protein domains connected by unstructured peptide sequences. These domains unfold when the protein is stretched and refold when the tension is removed.

<span class="mw-page-title-main">Fibril</span> Thin Fibre

Fibrils are structural biological materials found in nearly all living organisms. Not to be confused with fibers or filaments, fibrils tend to have diameters ranging from 10–100 nanometers. Fibrils are not usually found alone but rather are parts of greater hierarchical structures commonly found in biological systems. Due to the prevalence of fibrils in biological systems, their study is of great importance in the fields of microbiology, biomechanics, and materials science.

<span class="mw-page-title-main">Fusion protein</span> Protein created by joining other proteins into a single polypeptide

Fusion proteins or chimeric (kī-ˈmir-ik) proteins are proteins created through the joining of two or more genes that originally coded for separate proteins. Translation of this fusion gene results in a single or multiple polypeptides with functional properties derived from each of the original proteins. Recombinant fusion proteins are created artificially by recombinant DNA technology for use in biological research or therapeutics. Chimeric or chimera usually designate hybrid proteins made of polypeptides having different functions or physico-chemical patterns. Chimeric mutant proteins occur naturally when a complex mutation, such as a chromosomal translocation, tandem duplication, or retrotransposition creates a novel coding sequence containing parts of the coding sequences from two different genes. Naturally occurring fusion proteins are commonly found in cancer cells, where they may function as oncoproteins. The bcr-abl fusion protein is a well-known example of an oncogenic fusion protein, and is considered to be the primary oncogenic driver of chronic myelogenous leukemia.

<span class="mw-page-title-main">Arthropod exoskeleton</span>

Arthropods are covered with a tough, resilient integument, cuticle or exoskeleton of chitin. Generally the exoskeleton will have thickened areas in which the chitin is reinforced or stiffened by materials such as minerals or hardened proteins. This happens in parts of the body where there is a need for rigidity or elasticity. Typically the mineral crystals, mainly calcium carbonate, are deposited among the chitin and protein molecules in a process called biomineralization. The crystals and fibres interpenetrate and reinforce each other, the minerals supplying the hardness and resistance to compression, while the chitin supplies the tensile strength. Biomineralization occurs mainly in crustaceans. In insects and arachnids, the main reinforcing materials are various proteins hardened by linking the fibres in processes called sclerotisation and the hardened proteins are called sclerotin. The dorsal tergum, ventral sternum, and the lateral pleura form the hardened plates or sclerites of a typical body segment.

Epstein–Barr virus (EBV) latent membrane protein 2 (LMP2) are two viral proteins of the Epstein–Barr virus. LMP2A/LMP2B are transmembrane proteins that act to block tyrosine kinase signaling. LMP2A is a transmembrane protein that inhibits normal B-cell signal transduction by mimicking an activated B-cell receptor (BCR). The N-terminus domain of LMP2A is tyrosine phosphorylated and associates with Src family protein tyrosine kinases (PTKs) as well as spleen tyrosine kinase (Syk). PTKs and Syk are associated with BCR signal transduction.

<span class="mw-page-title-main">WW domain</span>

The WW domain is a modular protein domain that mediates specific interactions with protein ligands. This domain is found in a number of unrelated signaling and structural proteins and may be repeated up to four times in some proteins. Apart from binding preferentially to proteins that are proline-rich, with particular proline-motifs, [AP]-P-P-[AP]-Y, some WW domains bind to phosphoserine- and phosphothreonine-containing motifs.

<span class="mw-page-title-main">Abductin</span>

Abductin is a naturally occurring elastomeric protein found in the hinge ligament of bivalve mollusks. It is unique as it is the only natural elastomer with compressible elasticity, as compared to resilin, spider silk, and elastin. Its name was proposed from the fact that it functions as the abductor of the valves of bivalve mollusks.

Elastin-like polypeptides (ELPs) are synthetic biopolymers with potential applications in the fields of cancer therapy, tissue scaffolding, metal recovery, and protein purification. For cancer therapy, the addition of functional groups to ELPs can enable them to conjugate with cytotoxic drugs. Also, ELPs may be able to function as polymeric scaffolds, which promote tissue regeneration. This capacity of ELPs has been studied particularly in the context of bone growth. ELPs can also be engineered to recognize specific proteins in solution. The ability of ELPs to undergo morphological changes at certain temperatures enables specific proteins that are bound to the ELPs to be separated out from the rest of the solution via experimental techniques such as centrifugation.

<span class="mw-page-title-main">Kristi Kiick</span> American chemical engineer

Kristi Lynn Kiick is the Blue and Gold Distinguished Professor of Materials Science and Engineering at the University of Delaware. She studies polymers, biomaterials and hydrogels for drug delivery and regenerative medicine. She is a Fellow of the American Chemical Society, the American Institute for Medical and Biological Engineering, and of the National Academy of Inventors. She served for nearly eight years as the deputy dean of the college of engineering at the University of Delaware.

<span class="mw-page-title-main">Dityrosine</span> Chemical compound

Dityrosine is a dimeric form of tyrosine. Whereas tyrosine itself is a proteinogenic amino acid, dityrosine is non-proteinogenic. Various enzymes, such as CYP56A1 and myeloperoxidase, catalyze the oxidation of tyrosine residues in protein chains to form dityrosine crosslinks in various organisms. It was first isolated from rubber protein of locust wing ligament. Its formation can also be induced by various radical-forming agents.

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