Molecular Structure Of Collagen Research Articles

Impact of changes in collagen construction and molecular state on integrin – binding properties

The interaction between the integrin and collagen is important in cell adhesion and signaling. Collagen, as the main component of extracellular matrix, is a base material for tissue engineering constructs. In tissue engineering, the collagen structure and molecule state may be altered to varying degrees in the process of processing and utilizing, thereby affecting its biological properties. In this work, the impact of changes in collagen structure and molecular state on the binding properties of collagen to integrin α2β1 and integrin specific cell adhesion were explored. The results showed that the molecular structure of collagen is destroyed under the influence of heating, freeze-grinding and irradiation, the triple helix integrity is reduced and molecular breaking degree is increased. The binding ability of collagen to integrin α2β1 is increased with the increase of triple helix integrity and decays exponentially with the increase of molecular breaking degree. The collagen molecular state can also influences the binding ability of collagen to cellular receptor. The collagen fibrils binding to integrin α2β1 and HT1080 cells is stronger than to collagen monomolecule. Meanwhile, the hybrid fibril exhibits a different cellular receptor binding performance from corresponding single species collagen fibril. These findings provide ideas for the design and development of new collagen-based biomaterials and tissue engineering research.

Effects of γ-ray irradiation on the molecular structure of collagen in different product forms

Multi-dimensional systematic comparison of radiation tolerance of collagen molecules in different product forms.

Detergent-Free Decellularization Preserves the Mechanical and Biological Integrity of Murine Tendon.

Tissue decellularization has demonstrated widespread applications across numerous organ systems for tissue engineering and regenerative medicine applications. Decellularized tissues are expected to retain structural and/or compositional features of the natural extracellular matrix (ECM), enabling investigation of biochemical factors and cell-ECM interactions that drive tissue homeostasis, healing, and disease. However, the dense collagenous tendon matrix has limited the efficacy of traditional decellularization strategies without the aid of harsh chemical detergents and/or physical agitation that disrupt tissue integrity and denature proteins involved in regulating cell behavior. In this study, we adapted and established the advantages of a detergent-free decellularization method that relies on latrunculin B actin destabilization, alternating hypertonic-hypotonic salt and water incubations, nuclease-assisted elimination of cellular material, and protease inhibitor supplementation under aseptic conditions. Our method maintained the collagen molecular structure (i.e., minimal extent of denaturation), while adequately removing cells and preserving bulk mechanical properties. Furthermore, we demonstrated that decellularized tendon ECM-derived coatings isolated from different mouse strains, injury states (i.e., naive and acutely injured/"provisional"), and anatomical sites harness distinct biochemical cues and robustly maintain tendon cell viability in vitro. Together, our work provides a simple and scalable decellularization method to facilitate mechanistic studies that will expand our fundamental understanding of tendon ECM and cell biology. Impact statement In this study, we present a decellularization method for tendon that does not rely on any detergent or physical processing techniques. We assessed the impact of detergent-free decellularization using tissue, cellular, and molecular level analyses and validated the preservation of gross fiber architecture, collagen molecular structure, and extracellular matrix (ECM)-associated biological cues that are essential for studying physiological cell-ECM interactions. Finally, we demonstrated the applicability of this method for healthy and injured tendon environments, across mouse strains, and for different types of tendons, illustrating the utility of this approach for isolating the contributions of biochemical cues within unique tendon ECM microenvironments.

Evolution of conformation and thermal properties of bovine hides collagen in the sodium sulphide solution

Conformations of secondary and super secondary structure from bovine hides collagen are very important for constructing collagen molecular space structure, and directly related to its properties. In this work, the evolutional mechanism of the collagen conformation in the environment of sodium sulphide (Na2S) solution is periodically studied by FT-IR spectroscopy, the Gaussian peak fitting of secondary derivative, and auxiliary methods such as SDS-PAGE, SEM and TG. As a result, the three polypeptide chains structure of bovine hide collagen was hardly affected by the ions of OH−, HS− and S2−. The conformation of collagen molecules such as β-turn, triple helix and β-strand were gradually evolved into unordered structure and α-helix with the sequential addition of OH−, HS− and S2−, which is because the hydrogen bond inside collagen molecular is extended or opened with the increase of the synergistic effect of pH and reducibility of HS− and S2− in the solution. The bound water content and thermal properties of the treated collagen molecules are decreased. Finally, the order of the hydrolysis ability to collagen is NaOH < NaHS < Na2S at the same condition, which was confirmed by measuring the content of hydroxyproline from their solutions after treating the collagen. This work provides very important information for understanding the evolutional mechanism of bovine hide collagen conformation in the Na2S solution, developing the alternatives of sulfide, extraction of collagen, tanning, and application of collagen in biological and material science.

Micro-DSC, FTIR-ATR and NMR MOUSE study of the dose-dependent effects of gamma irradiation on vegetable-tanned leather: The influence of leather thermal stability

Leather artefacts, archaeological, historical or modern, are prone to microbiological attack which could lead to irreversible degradation. Previous studies performed on new leather mock-ups indicated good resistance of leather at doses up to (25–50) kGy. The aim of this research is to improve our understanding about the changes in the thermal stability and structural order of collagen within vegetable-tanned leather exposed to gamma irradiation. Variously vegetable-tanned leather samples were therefore exposed to irradiation with Co-60 gamma-rays with increasing doses (10–100 kGy) and the dose-dependent effect on collagen-tannin matrix was investigated using micro-DSC, the best technique for determining proteins' thermal stability, coupled with FTIR-ATR and NMR MOUSE spectroscopy, to enhance the analytical coverage of the calorimetric profile. FTIR-ATR technique revealed the very subtle changes in collagen at the molecular (lower order) level by, which are reflected in the properties of the structures with a higher level of order, namely the hydrothermal stability of fibrils (measured by micro-DSC) and mobility of macromolecular chains (determined by NMR MOUSE). It was proved that a 10 kGy dose causes significant variation on collagen molecular structure, fibrils hydrothermal stability, and macromolecular chain's mobility when the collagen-tannin matrix is already thermally destabilized and present a wide distribution of collagen populations with distinct thermal stability. On the other hand, leathers characterized by high thermal stability and homogeneous distribution of collagen populations better withstood radiation up to either 25 kGy or 50 kGy, depending on the collagen-tannin interactions' strength. This protocol, with high analytical and diagnostic sensitivity, can thus be applied to characterize a broader range of collagen materials sterilized/crosslinked with gamma radiation.

Chain substitution caused sub-fibril level differences in electromechanical structure and property of wild-type and oim/oim collagen fibers

Electromechanical changes in type I collagen caused by diseases are pivotal for monitoring bone health and offering informative message of constructing biobased smart devices. Here, we employ a mouse model of osteogenesis imperfecta (oim/oim), which is genetically modified through mutating the α-2 chain to α-1 chain in the collagen fibrils of the wild-type model (+/+ or heterotrimer), resulting in three α-1 chains in the collagen fibrils (i.e., homotrimer). Piezoresponse force microscopy (PFM) is used to directly visualize the sub-micrometer structures and piezoresponses of +/+ and oim/oim collagen fibers. Results show that the compact and highly ordered +/+ collagen fibers possess larger in-plane piezoresponses than the loosely packed and randomly distributed oim/oim collagen fibers. The mean values of the lateral PFM amplitude are 108.53 pm and 77.72 pm with interquartile ranges of 98.56–117.47 pm and 71.21–85.93 pm for +/+ and oim/oim collagen fibers, respectively. Molecular simulations demonstrate that the structural stability and electrically induced activity of heterotrimer are better than those of homotrimer, suggesting better biopiezoelectricity of comprising diverse polar residues (atomic charges) within the oriented heterotrimeric collagen molecular structure. Our study provides a new insight into the functional changes of human osteogenesis imperfecta.

Подходы к диагностике и ведению пациентов с гипермобильным типом синдрома Элерса — Данло

This review provides information about the patterns of the pathogenesis, clinical picture of Ehlers-Danlos syndrome (EDS), as well as the diagnosis and treatment of hypermobile type. Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited autosomal dominant diseases characterized by the development disorder of the collagen molecular structure, which leads to joint hypermobility, hyperelastic skin and its vulnerability, as well as advanced fragility of the entire body’s tissues. The clinical picture of EDS hypermobile type is dominated by musculoskeletal signs, characterized by joint hypermobility, arthralgias, dorsalgias, spontaneous joint dislocations in combination with hyperelastic skin and its vulnerability. The criteria presented in the 2017 EDS clinical classification are applied in order to make a diagnosis. Timely diagnosis of the hypermobile type of EDS syndrome contributes to early detection of changes in other organs and systems: aortic root dilation, mitral valve prolapse, abdominal hernias, pelvic organ prolapse, and others. Treatment methods include medication, physiotherapy, and surgery, the individual choice of which depends on the specific disease manifestations, the intensity and duration of pain. Competent selection of examination methods and treatment for patients with EDS hypermobil type can effectively stop chronic pain of the musculoskeletal syndrome and prevent severe disabling complications concerning internal organs.KEYWORDS: joint hypermobility, chronic pain, Ehlers-Danlos syndrome, hyperelastic skin, spontaneous dislocations, arthralgia.FOR CITATION: Viktorova I.A., Ivanova D.S., Kochimov R.Sh., Adyrbayev A.M. Methods for the diagnosis and management of patients with hypermobile Ehlers-Danlos syndrome. Russian Medical Inquiry. 2020;4(8):498–503. DOI: 10.32364/2587-6821-2020-4-8-498-503.

Effects of ex vivo ionizing radiation on collagen structure and whole-bone mechanical properties of mouse vertebrae.

Bone can become brittle when exposed to ionizing radiation across a wide range of clinically relevant doses that span from radiotherapy (accumulative 50 Gy) to sterilization (~35,000 Gy). While irradiation-induced embrittlement has been attributed to changes in the collagen molecular structure, the relative role of collagen fragmentation versus non-enzymatic collagen crosslinking remains unclear. To better understand the effects of radiation on the bone material without cellular activity, we conducted an ex vivo x-ray radiation experiment on excised mouse lumbar vertebrae. Spinal tissue from twenty-week old, female, C57BL/6J mice were randomly assigned to a single x-ray radiation dose of either 0 (control), 50, 1000, 17,000, or 35,000 Gy. Measurements were made for collagen fragmentation, non-enzymatic collagen crosslinking, and both monotonic and cyclic-loading compressive mechanical properties. We found that the group differences for mechanical properties were more consistent with those for collagen fragmentation than for non-enzymatic collagen crosslinking. Monotonic strength at 17,000 and 35,000 Gy was lower than that of the control by 50% and 73% respectively, (p < 0.001) but at 50 and 1000 Gy was not different than the control. Consistent with those trends, collagen fragmentation only occurred at 17,000 and 35,000 Gy. By contrast, non-enzymatic collagen crosslinking was greater than control for all radiation doses (p < 0.001). All results were consistent both for monotonic and cyclic loading conditions. We conclude that the reductions in bone compressive monotonic strength and fatigue life due to ex vivo ionizing radiation are more likely caused by fragmentation of the collagen backbone than any increases in non-enzymatic collagen crosslinks.

Collagen Structure-Function Relationships from Solid-State NMR Spectroscopy.

The extracellular matrix of a tissue is as important to life as the cells within it. Its detailed molecular structure defines the environment of a tissue's cells and thus their properties, including differentiation and metabolic status. Collagen proteins are the major component of extracellular matrices. Self-assembled collagen fibrils provide both specific mechanical properties to handle external stresses on tissues and, at the molecular level, well-defined protein binding sites to interact with cells. How the cell-matrix interactions are maintained against the stresses on the tissue is an important and as yet unanswered question. Similarly, how collagen molecular and fibrillar structures change in aging and disease is a crucial open question. Solid-state NMR spectroscopy offers insight into collagen molecular conformation in intact in vivo and in vitro tissues, and in this Account we review how NMR spectroscopy is beginning to provide answers to these questions. In vivo 13C,15N labeling of the extracellular matrix has given insight into collagen molecular dynamics and generated multidimensional NMR "fingerprints" of collagen molecular structure that allow comparison of local collagen conformation between tissues. NMR studies have shown that charged collagen residues (Lys, Arg) adopt extended-side-chain conformations in the fibrillar structure to facilitate charge-charge interactions between neighboring collagen molecules, while hydrophobic residues (Leu, Ile) fold along the collagen molecular axis to minimize the hydrophobic area exposed to surrounding water. Detailed NMR and molecular modeling work has shown that the abundant Gly-Pro-Hyp (Hyp = hydroxyproline) triplets in collagen triple helices confer well-defined flexibility because the proline is conformationally metastable, in contrast to the expectation that these triplets confer structural rigidity. The alignment of the Gly-Pro-Hyp triplets within the fibril structure means that the Gly-Pro-Hyp molecular flexibility generates fibril flexibility. The fibrillar bands of Gly-Pro-Hyp are highly correlated with collagen ligand binding sites, leading to the hypothesis that the fibril alignment of Gly-Pro-Hyp triplets is essential to protect collagen-ligand binding against external stresses on the tissue. Non-enzymatic chemistry between collagen side-chain amine groups (Lys, Arg) and reducing sugars-glycation-is an important source of matrix structural change in aging and disease. Glycation leads to stiffening of collagen fibrils, which is widely speculated to be the result of intermolecular cross-linking. The chemistry of non-enzymatic glycation has been extensively detailed through NMR studies and has been shown to lead to side-chain modifications as the majority reaction products, rather than intermolecular cross-links, with resultant molecular misalignment in the fibrils. Thus, a picture is beginning to emerge in which collagen glycation causes stiffening through misalignment of collagen molecular flexible regions rather than intermolecular cross-linking, meaning that new thinking is needed on how to alleviate collagen structural changes in aging and disease.

Wavelength-Dependent Second Harmonic Generation Circular Dichroism for Differentiation of Col I and Col III Isoforms in Stromal Models of Ovarian Cancer Based on Intrinsic Chirality Differences.

Extensive remodeling of the extracellular matrix (ECM) occurs in many epithelial cancers. For example, in ovarian cancer, upregulation of collagen isoform type III has been linked to invasive forms of the disease, and this change may be a potential biomarker. To examine this possibility, we implemented wavelength-dependent second harmonic generation circular dichroism (SHG-CD) imaging microscopy to quantitatively determine changes in chirality in ECM models comprised of different Col I/Col III composition. In these models, Col III was varied between 0 and 40%, and we found increasing Col III results in reduced net chirality, consistent with structural biology studies of Col I and III in tissues where the isoforms comingle in the same fibrils. We further examined the wavelength dependence of the SHG-CD to both optimize the response and gain insight into the underlying mechanism. We found using shorter SHG excitation wavelengths resulted in increased SHG-CD sensitivity, where this is consistent with the electric-dipole-coupled oscillator model suggested previously for the nonlinear chirality response from thin films. Moreover, the sensitivity is further consistent with the wavelength dependency of SHG intensity fit to a two-state model of the two-photon absorption in collagen. We also provide experimental calibration protocols to implement the SHG-CD modality on a laser scanning microscope. We last suggest that the technique has broad applicability in probing a wide range of diseased states with changes in collagen molecular structure.

Inhibitors of thermally induced burn incidents – the examinations of the flammability, TGA, SAXS and SEM methods

The examinations of the skin flammability, small-angle X-ray scattering (SAXS) and thermogravimetric (TGA) investigations were all carried out in temperature sufficient for simulating a burn incident. Above methods were used to perform assessment of collagen molecular structure changes in conditions of thermal oxidative stress, whereas the scanning electron microscopy analysis (SEM) was used to illustrate skin surface changes. The changes were observed in the presence of active antioxidants such as L-ascorbic acid, sodium ascorbate and hydrogel of orthosilicic acid H4SiO4 • n H2O. Presence of these modifiers of the burn process minimizes external effects of simulated burn incidents for model samples of animal skin and burn wound epidermis extracted from the patients. The examinations of the skin flammability were carried out with the limited oxygen index (LOI) method. In this study, synergy between orthosilicic acid and L-ascorbic acid and sodium ascorbate into animal and human skin has been shown through an increase in LOI values. The treatment by means of L-ascorbic acid affects particular morphological changes in the skin which is visible in SEM method. Skin samples incubated in the solution of the 3.5 %, 5 % L-ascorbic acid, 7 % sodium ascorbate solutions and 7 % orthosilicic acid demonstrate the development of a structure resembling a coherent solid composite. SAXS gives structural information on the assembly of dermal collagen as well as the lamellar organization of stratum corneum (SC) lipids located in the outermost part of the epidermis. Using this technique, two lamellar phases with repeat distance of approximately 4.3 and 6 nm in the SC lipids domains were observed. Moreover, the diameter of the collagen fibrils were extracted. The observed differences in the values of these parameters allowed us to better understand the mechanism of modification of the surface of the burn affected skin and the influence of the modification on the process of skin regeneration.

The features of infrared spectrum of bio-polymer and its theoretical investigation

We have here an insight into the features of molecular structures of bio-polymers with α-helix structure using infrared spectrum and elucidated theoretically, its relationship with bio-functions. In this case, we analyzed first the features of molecular structure of collagen and collected further the infrared spectrum of absorption of collagen and bovine serum albumin containing α-helix conformation in 400–4000 cm-1 as well as their changes of strength of infrared absorption with varying temperatures using Fourier Transform–Infrared (FT-IR) spectrometers in the region of 15–95°C. The results show that there is a new band of 1650 cm-1 close to the amide-I band of 1666 cm-1 or 1670 cm-1 in these bio-polymers, its strength decreases exponentially with increasing temperature of the systems, which can be expressed by exp [-(0.437 + 8.987 × 10-6  T 2)], but 1666 cm-1 band increases linearly with increasing temperature. We calculated the energy spectrum of the protein molecules with α-helix conformation using the Soliton Theory of bio-energy transport, which are basically same with the experimental results measured by us. From these results and soliton theory we can conclude that the nonlinear soliton excitation, corresponding to 1650 cm-1 band and the exciton excitation, is related to 1666 cm-1 band, exists in the collagen and bovine serum albumin. In the meanwhile, these results also verified that the soliton theory of bio-energy transport along α-helix bio-polymers is appropriate to the protein molecules with α-helix conformation. Therefore, the studied results are helpful to elucidate the relationship between the molecular structure and bio-function of these bio-polymers.

Octacalcium phosphate - a metastable mineral phase controls the evolution of scaffold forming proteins.

The molecular structure of collagen type 1 can be understood as the result of evolutionary selection in the process of formation of calcium phosphate based biocomposites acting as load bearing components in living organisms. The evolutionary selection fulfills the principle of 'survival of the fittest' in a particular biological environment. Disk-like post-nucleation complexes of Ca2(HPO4)3 2- organized in ribbon-like assemblies in the metastable octacalcium phosphate (OCP) phase, and Ca3 triangles in the stable HAP phase had formed the crystallographic motifs in this selection process. The rotational as well as the translational symmetry of the major tropocollagen (TC) helix agree nearly perfectly with the corresponding symmetries of the OCP structure. The sequence of (Gly-X-Y) motifs of the three α chains constituting the TC molecule enables an optimized structural fit for the nucleation of Ca3 triangles, the directed growth of nanostructured OCP, and the subsequent formation of hydroxyapatite (HAP) in collagen macrofibrils by a topotaxial transition. The known connection between genetic defects of collagen type 1 and Osteogenesis imperfecta should motivate the search for similar dependences of other bone diseases on a disturbed molecular structure of collagen on the genetic scale.

Exploring the dermal “template effect” and its structure

Scar formation is the problem for clinic surgery. Recent studies showed that the scar formation was closely related to the dermal defect. Three-dimensional (3-d) structures of dermal tissues act as a template to modulate cell functions that are essential the regeneration of skin structure and function. The dermal tissue's integrity and continuity is a prerequisite for repair to take place. Loss of the dermal tissue integrity and continuity due to trauma leads to a lack of the template effect, which may be one important mechanism that hinders the recovery of cell function, resulting in scar formation. These studies give us two questions: what is the three-dimensional (3-d) structure of the dermal tissue? How do the tissues form? Up to now, it is well known that the molecular structure of collagen, the micro-structure of microfibril, however, the mesoscopic structure of dermal tissues is still unclear. Our recently rudimentary studies showed the problem might be resolved by phase-contrast micro-tomography with synchrotron radiation, which is likely to open new avenues for further investigations on wound regeneration and skin tissue engineering.

Using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR FT-IR) to Study the Molecular Conformation of Parchment Artifacts in Different Macroscopic States

Maintaining appropriate temperatures and relative humidity is considered essential to extending the useful life of parchment artifacts. Although the relationship between environmental factors and changes to the physical state of artifacts is reasonably understood, an improved understanding of the relationship between the molecular conformation and changes to the macroscopic condition of parchment is needed to optimize environmental conditions. Using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FT-IR) analysis, the conformation of the molecular structure in selected parchment samples with specific macroscopic conditions, typically discoloration and planar deformations (e.g., cockling and tearing), have been made. The results of this investigation showed that the Fourier transform infrared signal differs for parchment samples exhibiting different macroscopic conditions. In areas exhibiting planar deformation, a change in the Fourier Transform Infrared signal was observed that indicates unfolding of the molecular conformation. In comparison, the discolored samples showed a change in molecular conformation that indicates a chemical change within the collagen molecular structure. This paper discusses the possible causal associations and implications of these findings for the conservation and preservation of parchment artifacts.

コラーゲンの構造

The molecular structure of collagen has long been believed to be that of a triple-stranded 10/3 helix (the Rich and Crick model). The meager X-ray diffraction data from native collagen can, however, also be explained in terms of a triple-stranded 7/2 helical model. The recent single-crystal study of the (Gly-Pro-Hyp)9 peptide confirmed that this peptide, which contains the Gly-Pro-Hyp sequence that is used as a basic repeating unit of the Rich and Crick model, does not adopt a 10/3 helix structure, but does adopt a 7/2 helix. The resulting structure will be useful for understanding molecular interactions involving collagen.

Molecular structure of tail tendon fibers in TIEG1 knockout mice using synchrotron diffraction technology

The purpose of this study was to characterize the effect of TIEG1 on the molecular structure of collagen within tail tendon fibers using 3-mo-old female C57BL/6 wild-type (WT) and TIEG1 KO mice. Synchrotron X-ray microdiffraction experiments were carried out on single tendon fibers extracted from the WT and TIEG1 KO dorsal tail tendon. The fibers were scanned in the radial direction, and X-ray patterns were obtained. From these patterns, the meridional direction was analyzed through X-ray intensity profile. In addition, collagen content was investigated using hydroxyproline assays, and qualitative real-time PCR experiments were performed on RNA isolated from fibroblasts to examine specific gene expression changes. The results showed different X-ray diffraction patterns between WT and TIEG1 KO tendon fibers, indicating a disorganization of the collagen structure for the TIEG1 KO compared with WT mice. Furthermore, the analyses of the X-ray intensity profiles exhibited a higher (23 A) period of collagen for the TIEG1 KO compared with the WT mice. The results of the hydroxyproline assays revealed a significant decrease in the TIEG1 KO compared with WT mice, leading to a decrease in the total amount of collagen present within the TIEG1 KO tendons. Moreover, qualitative real-time PCR results showed differences in the expression profiles of specific genes known to play important roles in tendon fiber development. These data further elucidate the role of TIEG1 on tendon structure and could explain the previous defects in the structure-function relationship found for TIEG1 KO tendon fibers.

SU‐GG‐I‐128: Biophysical Studies of Tendon to Elucidate Magic Angle MRI

Purpose: The “Magic Angle Effect” observed in cartilage, tendon and other collagen rich tissues of the extracellular matrix have largely unused potential for evaluation of musculo‐skeletal disease processes. These studies seek to improve understanding of the molecular basis for magic angle phenomena based on collagen hydration. We hypothesize that improved understanding will provide a conceptual framework and extend the ability of musculo‐skeletal radiologists to design protocols using MRI orientational contrast for better accuracy and specificity. Method and Materials: These studies use Differential Scanning Calorimetry (DSC) to directly measure the enthalpy and entropy of water bound to rat tail collagen/tendon at different hydration levels. Water vapor sorption and recovery rehydration rates of rat tail collagen/tendon at 22 °C were also measured. Measured bound water fractions are compared to the theoretical values (h=0.263 g/g) predicted from the molecular structure of collagen. Bound water hydration measured with both methods agreed with the molecular prediction of water bound to the protein back bone. Statistical analyses performed using Graphpad Prism. Results: The water vapor sorption and DSC studies of collagen/tendon at 22 °C show that both equilibrium hydration and enthalpy are linear functions of relative humidity up to critical hydration of the protein backbone h = 0.26 g/g. The water bridge hydration hypothesis identifies three hydration water fractions in direct contact with the protein that differ in motional/orientational properties from bulk water. Comparison to T1 and T2 relaxation rate and orientational studies shows the relaxation rate of tendon is determined by fast exchange of water between these motional and orientational restricted water fractions. Conclusion: This work offers evidence for the important role of protein main chain hydration in determining MRI contrast due to dielectric binding of polar water molecules interacting with partial electric charges separated on the backbone by steric restrictions of the collagen molecule.

The Role of Type I Collagen Molecular Structure in Tendon Elastic Energy Storage

AbstractIn order to facilitate locomotion and limb movement many animals store energy elastically in their tendons. The formation of crosslinked collagen fibers in tendons results in the conversion of weak, liquid-like embryonic tissues into tough elastic solids that can store energy and perform work. Collagen fibers in the form of fascicles are the major structural units found in tendons. The purpose of this paper is to review the literature on collagen self-assembly and tendon development and to relate this information to the development of elastic energy storage in nonmineralizing and mineralizing tendons. Of particular interest is the mechanism by which energy is stored in tendons during locomotion. In the turkey, much of the force generated by the gastrocnemius muscle is stored as elastic energy during tendon deformation and not within the muscle. As limbs move, the tendons are strained, causing the collagen fibers in the extracellular matrices to stretch. Through the analysis of turkey tendons, collagen fibers, and a molecular model, it is hypothesized that elastic energy is stored in the flexible regions of the collagen molecule. Data from the molecular model, mineralized fibers, and turkey tendons show that the presence of calcium and phosphate ions causes an increase in elastic energy stored per unit strain. Based on the theoretical modeling studies, the increase in stress with strain is a result of the initiation of stretching of the rigid regions of collagen molecules.

Age dependence of in situ termostability of collagen in human bone.

The hypothesis of this study is that the in situ thermostability of collagen in bone changes with age and such changes relate to the structural properties of collagen and/or the interaction between the collagen and mineral phases. To test the hypothesis, the effect of age on the in situ thermostability of collagen in human bone and its correlation with the mineral and collagen phases were investigated. In this study, 30 human cadaveric femurs were collected and divided into three age groups: young adults (20-45 years), middle aged (46-69 years), and elderly (over 70 years of age). The in situ thermostability of collagen was assessed using high performance liquid chromatography (HPLC) in terms of the amount of heat-induced collagen denaturation at eight temperatures between 25 degrees C and 140 degrees C. In addition to the density and weight fraction of the mineral and organic phases, the concentration of collagen crosslinks was measured to assess the structural integrity of collagen. The results of this study indicate that the in situ thermostability of collagen increases with increasing age, and such age-related changes correlate with the following: collagen molecular structure, amount of noncalcified collagen, and the fraction and density of the mineral phase in bone. These results suggest that the age-related changes in the in situ thermostability of collagen most likely relate to the collagen structure and its interaction with the mineral phase. In addition, the bone remodeling process may play a role in the age-related changes in collagen thermostability because noncalcified collagen is commonly associated with this process.