Fibroins
Silk
Bombyx
Sericins
Spiders
Exocrine Glands
Biocompatible Materials
Tissue Scaffolds
Keratins
Hoof and Claw
Encyclopedias as Topic
Perissodactyla
Intermediate Filaments
Reptiles
Gene targeting in the silkworm by use of a baculovirus. (1/232)
The Bombyx mori fibroin light (L)-chain gene was cloned and the green fluorescent protein (GFP) gene inserted into exon 7. The chimeric L-chain-GFP gene was used to replace the polyhedrin gene of Autographa californica nucleopolyhedrovirus (AcNPV). This recombinant virus was used to target the L-chain-GFP gene to the L-chain region of the silkworm genome. Female moths were infected with the recombinant virus and then mated with normal male moths. Genomic DNA from their progenies was screened for the desired targeting event. This analysis showed that the chimeric gene had integrated into the L-chain gene on the genome by homologous recombination and was stably transmitted through generations. The chimeric gene was expressed in the posterior silk gland, and the gene product was spun into the cocoon layer. (+info)Fibroin allergy. IgE mediated hypersensitivity to silk suture materials. (2/232)
Delayed-type hypersensitivity with granulomatous lesions to silk sutures is rather rare. Yet, braided silk sutures often act as a non-immunologic foreign-body and cause a granulomatous inflammatory reaction years after surgery. We report here a case of recurrent granulomas with remarkable infiltration of eosinophils that may have resulted from an IgE-mediated hypersensitivity reaction to silk fibroin, a component of the braided silk suture. Under normal circumstances exposure to fibroin is rather rare. Therefore, the present patient may have developed this reaction to the silk sutures used in a previous surgery. (+info)Studies on silk fibroin of Bombyx mori. I. Fractionation of fibroin prepared from the posterior silk gland. (3/232)
1. Fractionation of fibroin prepared from the posterior silk glands of Bombyx mori was carried out. After carboxymethylation of the fibroin, it was fractionated by ammonium sulfate precipitation, Sephadex G-200 gel filtration and DEAE-cellulose column chromatography. 2. The fibroin was composed of at least two protein groups of large molecular size and three or four components of small molecular size, and, in addition, a mixture of proteins ranging in size from about 25,000 to more than 100,000 daltons with almost the same amino acid compositions. 3. The latter proteins contained about 48% glycine, 32% alanine, 11% serine, 4.5% tyrosine, 2% valine, and other minor amino acids. The sum of these main five amino acids accounts for more than 97% of the total amino acid residues of the proteins. 4. The present results indicate major heterogeneity in the molecular size of posterior silk gland fibroin, and, in addition, suggest the possibility of repeating sequences with relatively simple amino acid compositions in major peptide chains of fibroin. (+info)Determination of the site of disulfide linkage between heavy and light chains of silk fibroin produced by Bombyx mori. (4/232)
The analysis of fibroin secretion-deficient 'naked-pupa' mutant silkworms has suggested that the disulfide linkage between heavy (H) and light (L) chains of fibroin, produced by the silkworm, Bombyx mori, is essential in its efficient large-scale secretion from the posterior silk gland cells. However, the site of disulfide-linkage between H- and L-chains has not been determined. In this study, cysteine residues involved in the single disulfide linkage between H- and L-chains were identified as the twentieth residue from the carboxyl terminus of H-chain (Cys-c20) and Cys-172 of L-chain by sequencing of genomic clones and peptide analysis. Furthermore, Cys-c4 (fourth residue from the carboxyl terminus) and Cys-c1 at the carboxyl terminus of H-chain were shown to form an intramolecular disulfide bond. (+info)The mechanical design of spider silks: from fibroin sequence to mechanical function. (5/232)
Spiders produce a variety of silks, and the cloning of genes for silk fibroins reveals a clear link between protein sequence and structure-property relationships. The fibroins produced in the spider's major ampullate (MA) gland, which forms the dragline and web frame, contain multiple repeats of motifs that include an 8-10 residue long poly-alanine block and a 24-35 residue long glycine-rich block. When fibroins are spun into fibres, the poly-alanine blocks form (&bgr;)-sheet crystals that crosslink the fibroins into a polymer network with great stiffness, strength and toughness. As illustrated by a comparison of MA silks from Araneus diadematus and Nephila clavipes, variation in fibroin sequence and properties between spider species provides the opportunity to investigate the design of these remarkable biomaterials. (+info)Conformational transitions in model silk peptides. (6/232)
Protein structural transitions and beta-sheet formation are a common problem both in vivo and in vitro and are of critical relevance in disparate areas such as protein processing and beta-amyloid and prion behavior. Silks provide a "databank" of well-characterized polymorphic sequences, acting as a window onto structural transitions. Peptides with conformationally polymorphic silk-like sequences, expected to exhibit an intractable beta-sheet form, were characterized using Fourier transform infrared spectroscopy, circular dichroism, and electron diffraction. Polymorphs resembling the silk I, silk II (beta-sheet), and silk III (threefold polyglycine II-like helix) crystal structures were identified for the peptide fibroin C (GAGAGS repetitive sequence). Two peptides based on silk amorphous sequences, fibroin A (GAGAGY) and fibroin V (GDVGGAGATGGS), crystallized as silk I under most conditions. Methanol treatment of fibroin A resulted in a gradual transition from silk I to silk II, with an intermediate state involving a high proportion of beta-turns. Attenuated total reflectance Fourier transform infrared spectroscopy has been used to observe conformational changes as the peptides adsorb from solution onto a hydrophobic surface. Fibroin C has a beta-strand structure in solution but adopts a silk I-like structure upon adsorption, which when dried on the ZnSe crystal contains silk III crystallites. (+info)Correlation between mRNA structure of the coding region and translational pauses. (7/232)
Discontinuous translational elongation of polypeptides is observed during spider dragline silk fibroin synthesis (1,2). The repeating segment of one of the two subunit proteins constituting spider major ampullate (dragline) silk of Nephila clavipes, Spidroin 2, consists of alternate alanine-rich and proline-rich regions (3). It was found that the calculated free energy of the secondary structure of Spidroin 2 mRNA per nucleotide for the alanine-rich region is about the same as that for the successive proline-rich region. The small stability changes of local mRNA secondary structures along the mRNA chain suggest that the translational pauses observed for dragline silk fibroin synthesis may not be correlated with Spidroin 2 mRNA structure, in contrast to Spidroin 1 mRNA structure which may explain the translational pauses (4). (+info)Fine organization of Bombyx mori fibroin heavy chain gene. (8/232)
The complete sequence of the Bombyx mori fibroin gene has been determined by means of combining a shotgun sequencing strategy with physical map-based sequencing procedures. It consists of two exons (67 and 15 750 bp, respectively) and one intron (971 bp). The fibroin coding sequence presents a spectacular organization, with a highly repetitive and G-rich (approximately 45%) core flanked by non-repetitive 5' and 3' ends. This repetitive core is composed of alternate arrays of 12 repetitive and 11 amorphous domains. The sequences of the amorphous domains are evolutionarily conserved and the repetitive domains differ from each other in length by a variety of tandem repeats of subdomains of approximately 208 bp which are reminiscent of the repetitive nucleosome organization. A typical composition of a subdomain is a cluster of repetitive units, Ua, followed by a cluster of units, Ub, (with a Ua:Ub ratio of 2:1) flanked by conserved boundary elements at the 3' end. Moreover some repeats are also perfectly conserved at the peptide level indicating that the evolutionary pressure is not identical along the sequence. A tentative model for the constitution and evolution of this unusual gene is discussed. (+info)Fibroins are a type of protein that make up the structural component of silk fibers produced by certain insects and arachnids, such as silkworms and spiders. These proteins are characterized by their repetitive amino acid sequences, which give silk its unique properties of strength, flexibility, and toughness. Fibroins have been studied for their potential applications in biomedicine, including tissue engineering, drug delivery, and medical textiles.
I'm sorry for any confusion, but "Silk" is not a medical term. Silk is a natural protein fiber, mainly composed of fibroin and produced by certain insect larvae to form cocoons. It's commonly used in textiles and other industries for its softness, smoothness, and strength. If you have any questions related to medical terminology or health-related topics, I'd be happy to help with those instead!
"Bombyx" is a genus name that refers to a group of insects in the family Bombycidae, which are known as silk moths. The most well-known species in this genus is "Bombyx mori," which is the domesticated silkworm used for commercial silk production.
The term "Bombyx" itself does not have a specific medical definition, but it is sometimes used in medical or scientific contexts to refer to this group of insects or their characteristics. For example, researchers might study the effects of Bombyx mori silk on wound healing or tissue regeneration.
It's worth noting that while some species of moths and butterflies can be harmful to human health in certain circumstances (such as by acting as vectors for diseases), the Bombyx genus is not typically considered a medical concern.
Sericin is not a medical term per se, but it is a term used in the field of biochemistry and materials science. Sericins are a group of proteins that are found in silk fibers produced by certain insects, particularly silkworms (Bombyx mori). These proteins make up about 25-30% of the total weight of silk fibers and are responsible for the adhesive properties that allow silk fibers to stick together.
Sericins have been studied for their potential medical applications due to their unique chemical and physical properties. They have been found to possess various biological activities, such as antioxidant, anti-inflammatory, and wound healing properties. Some research has suggested that sericins may be useful in the development of new biomaterials for tissue engineering, drug delivery systems, and medical devices.
However, it is important to note that while sericins have shown promise in preclinical studies, more research is needed to establish their safety and efficacy in humans before they can be widely used in medical applications.
I'm sorry for any confusion, but "spiders" is not a term that has a specific medical definition. It is a common name used to refer to arachnids of the order Araneae, characterized by having two main body parts (the cephalothorax and abdomen), eight legs, and fangs that inject venom.
However, in a medical context, "spider" or "spider bite" may be used to describe skin lesions or reactions resulting from the bite of certain spiders, particularly those with medically significant venoms. For example, necrotic arachnidism is a condition caused by the bite of some spider species, such as recluse spiders (Loxosceles spp.). The bites can cause skin necrosis and other systemic symptoms in severe cases.
If you are looking for information on a specific medical topic or condition, please provide more details so I can offer a more accurate response.
Exocrine glands are a type of gland in the human body that produce and release substances through ducts onto an external or internal surface. These glands are responsible for secreting various substances such as enzymes, hormones, and lubricants that help in digestion, protection, and other bodily functions.
Exocrine glands can be further classified into three types based on their mode of secretion:
1. Merocrine glands: These glands release their secretions by exocytosis, where the secretory product is enclosed in a vesicle that fuses with the cell membrane and releases its contents outside the cell. Examples include sweat glands and mucous glands.
2. Apocrine glands: These glands release their secretions by pinching off a portion of the cytoplasm along with the secretory product. An example is the apocrine sweat gland found in the armpits and genital area.
3. Holocrine glands: These glands release their secretions by disintegrating and releasing the entire cell, including its organelles and secretory products. An example is the sebaceous gland found in the skin, which releases an oily substance called sebum.
Biocompatible materials are non-toxic and non-reacting substances that can be used in medical devices, tissue engineering, and drug delivery systems without causing harm or adverse reactions to living tissues or organs. These materials are designed to mimic the properties of natural tissues and are able to integrate with biological systems without being rejected by the body's immune system.
Biocompatible materials can be made from a variety of substances, including metals, ceramics, polymers, and composites. The specific properties of these materials, such as their mechanical strength, flexibility, and biodegradability, are carefully selected to meet the requirements of their intended medical application.
Examples of biocompatible materials include titanium used in dental implants and joint replacements, polyethylene used in artificial hips, and hydrogels used in contact lenses and drug delivery systems. The use of biocompatible materials has revolutionized modern medicine by enabling the development of advanced medical technologies that can improve patient outcomes and quality of life.
Tissue scaffolds, also known as bioactive scaffolds or synthetic extracellular matrices, refer to three-dimensional structures that serve as templates for the growth and organization of cells in tissue engineering and regenerative medicine. These scaffolds are designed to mimic the natural extracellular matrix (ECM) found in biological tissues, providing a supportive environment for cell attachment, proliferation, differentiation, and migration.
Tissue scaffolds can be made from various materials, including naturally derived biopolymers (e.g., collagen, alginate, chitosan, hyaluronic acid), synthetic polymers (e.g., polycaprolactone, polylactic acid, poly(lactic-co-glycolic acid)), or a combination of both. The choice of material depends on the specific application and desired properties, such as biocompatibility, biodegradability, mechanical strength, and porosity.
The primary functions of tissue scaffolds include:
1. Cell attachment: Providing surfaces for cells to adhere, spread, and form stable focal adhesions.
2. Mechanical support: Offering a structural framework that maintains the desired shape and mechanical properties of the engineered tissue.
3. Nutrient diffusion: Ensuring adequate transport of nutrients, oxygen, and waste products throughout the scaffold to support cell survival and function.
4. Guided tissue growth: Directing the organization and differentiation of cells through spatial cues and biochemical signals.
5. Biodegradation: Gradually degrading at a rate that matches tissue regeneration, allowing for the replacement of the scaffold with native ECM produced by the cells.
Tissue scaffolds have been used in various applications, such as wound healing, bone and cartilage repair, cardiovascular tissue engineering, and neural tissue regeneration. The design and fabrication of tissue scaffolds are critical aspects of tissue engineering, aiming to create functional substitutes for damaged or diseased tissues and organs.
I'm sorry for any confusion, but "Insect Proteins" is not a recognized medical term. However, I can provide some information about insect protein from a nutritional and food science perspective.
Insect proteins refer to the proteins that are obtained from insects. Insects are a rich source of protein, and their protein content varies by species. For example, mealworms and crickets have been found to contain approximately 47-63% and 60-72% protein by dry weight, respectively.
In recent years, insect proteins have gained attention as a potential sustainable source of nutrition due to their high protein content, low environmental impact, and the ability to convert feed into protein more efficiently compared to traditional livestock. Insect proteins can be used in various applications such as food and feed additives, nutritional supplements, and even cosmetics.
However, it's important to note that the use of insect proteins in human food is not widely accepted in many Western countries due to cultural and regulatory barriers. Nonetheless, research and development efforts continue to explore the potential benefits and applications of insect proteins in the global food system.
Keratins are a type of fibrous structural proteins that constitute the main component of the integumentary system, which includes the hair, nails, and skin of vertebrates. They are also found in other tissues such as horns, hooves, feathers, and reptilian scales. Keratins are insoluble proteins that provide strength, rigidity, and protection to these structures.
Keratins are classified into two types: soft keratins (Type I) and hard keratins (Type II). Soft keratins are found in the skin and simple epithelial tissues, while hard keratins are present in structures like hair, nails, horns, and hooves.
Keratin proteins have a complex structure consisting of several domains, including an alpha-helical domain, beta-pleated sheet domain, and a non-repetitive domain. These domains provide keratin with its unique properties, such as resistance to heat, chemicals, and mechanical stress.
In summary, keratins are fibrous structural proteins that play a crucial role in providing strength, rigidity, and protection to various tissues in the body.
I'm sorry for any confusion, but "Hoof and Claw" is not a medical term or condition. The term "hoof" refers to the hard covering on the toes of animals such as horses, cows, and other ungulates, while "claw" refers to the sharp nail-like structure found on the toes of animals such as cats, dogs, and birds.
If you have any questions related to medical terminology or health concerns, I would be happy to try to help answer them for you.
An encyclopedia is a comprehensive reference work containing articles on various topics, usually arranged in alphabetical order. In the context of medicine, a medical encyclopedia is a collection of articles that provide information about a wide range of medical topics, including diseases and conditions, treatments, tests, procedures, and anatomy and physiology. Medical encyclopedias may be published in print or electronic formats and are often used as a starting point for researching medical topics. They can provide reliable and accurate information on medical subjects, making them useful resources for healthcare professionals, students, and patients alike. Some well-known examples of medical encyclopedias include the Merck Manual and the Stedman's Medical Dictionary.
Perissodactyla is not a medical term, but rather a taxonomic order in zoology. It includes mammals with an odd number of toes on each foot and a particular type of digestive system called "hindgut fermentation." The order Perissodactyla includes horses, rhinos, and tapirs.
Intermediate filaments (IFs) are a type of cytoskeletal filament found in the cytoplasm of eukaryotic cells, including animal cells. They are called "intermediate" because they are smaller in diameter than microfilaments and larger than microtubules, two other types of cytoskeletal structures.
Intermediate filaments are composed of fibrous proteins that form long, unbranched, and flexible filaments. These filaments provide structural support to the cell and help maintain its shape. They also play a role in cell-to-cell adhesion, intracellular transport, and protection against mechanical stress.
Intermediate filaments are classified into six types based on their protein composition: Type I (acidic keratins), Type II (neutral/basic keratins), Type III (vimentin, desmin, peripherin), Type IV (neurofilaments), Type V (lamins), and Type VI (nestin). Each type of intermediate filament has a specific function and is expressed in different cell types. For example, Type I and II keratins are found in epithelial cells, while vimentin is expressed in mesenchymal cells.
Overall, intermediate filaments play an essential role in maintaining the structural integrity of cells and tissues, and their dysfunction has been implicated in various human diseases, including cancer, neurodegenerative disorders, and genetic disorders.
I'm sorry for any confusion, but "Reptiles" is not a medical term. It is a term used in biology to describe a class of cold-blooded, scaly-skinned animals that include snakes, lizards, alligators, crocodiles, turtles, and tortoises. They are characterized by having lungs for breathing, laying eggs on land, and having a three-chambered heart. If you have any medical questions or terms, I'd be happy to help clarify those!
Type II keratins are a group of intermediate filament proteins that are primarily expressed in epithelial cells. They are part of the keratin family, which is divided into two types (Type I and Type II) based on their acidic or basic isoelectric point. Type II keratins have a basic isoelectric point and include several subtypes such as KRT2, KRT3, KRT4, KRT10, KRT12, and others.
Type II keratins form heteropolymers with Type I keratins to provide structural support and integrity to epithelial cells. They are essential for the maintenance of cell shape, polarity, and mechanical resistance to stress. Mutations in type II keratin genes have been associated with several human genetic disorders, including epidermolysis bullosa simplex, a blistering skin disorder, and some forms of hair loss.
In summary, Type II keratins are a group of basic intermediate filament proteins that form heteropolymers with Type I keratins to provide structural support and integrity to epithelial cells.