Die Strukturdynamik von Sehnenfasern, d. h. die Ermittlung bestimmter Parameter an in Bewegung befindlichen Kollagenmolekülen, wird an nativen und an mit Hexamethylendiisocyanat (HMDI) künstlich vernetzten Sehnenfasern aufgezeigt. Das Ziel dieser Untersuchungen ist die analytische Erfassung und Lokalisation künstlich eingeführter Querbrücken mit Aussagewert für natürlicherweise vorkommende Vernetzungen. Voraussetzung hierfür ist der Einsatz neuer Technologien, so z. B. der Synchrotronstrahlung zur Erzeugung von Röntgenmeßdaten sehr schnell ablaufender dynamischer Vorgänge sowie die überraschende Tatsache, daß mit HMDI vernetzte Fasern ein von nativen Objekten nicht unterscheidbares Röntgendiagramm liefern.

Water has been found to be essential in the maintainance of collagen in its native conformation and is considered as an integral element of the collagen structure. The collagen triple helix differs from both the α-helix and the β-sheet structures in that not all hydrogen bonding sites on the backbone are occupied within the macromolecular structure. Only every third C=O and NH group of the backbone is involved in intramolecular hydrogen bonding. Water molecules stabilize the triple helical structure by intramolecular bridges by binding to the unoccupied hydrogen donor and acceptor groups on the protein backbone (Traub 1971; Ramachandran 1976).

Native collagen fibers were exposed to different dynamic loads to simulate damage to tendons and ligaments relevant clinically and for sports medicine. The results suggest that the rupture of a tendon is caused at the submicroscopic fibrillar level. Not only slow or very fast elongation, but also very fast unloading of stretched fibers seems to be responsible for disseminated damage, which reduces the stability of a fiber. This damage is induced by intrafibrillar sliding processes, which occur only a few seconds before macroscopic slippage takes place. The significance of these events for the beginning and progress of repair in vivo is discussed. The conclusions are supported by simultaneous mechanical and radiological measurements, as well as by light- and electron-microscopic results.

Small-angle x-ray diffraction spectra of dermatosparactic tendon collagen show a decreased intensity of the first order reflection. We interprete this finding to be due to the N-terminal propeptide which fills the intermolecular gap region partially.

Molecular rearrangements in native fibres of rat-tail tendons (RTT) and human finger flexor tendons are registered with the help of short time diffraction spectra using synchrotron radiation. There is a tension-induced increase of the 67 nm long period as well as changes in the intensities of some meridional small angle reflections (fig. 1). Both effects are reversible when unloading the fibre, but are preserved when the load is held constant until the fibre tears. The increase in the long period is due partly to an inhomogeneous molecular process as indicated by the change in the intensities and partly to a stretching of the triple helices themselves. The inhomogeneous behaviour is due to an increase of the D-stagger from 234 to for example 236 amino acid residues, caused by sliding of the triple helices relative to each other, which results in a change of the length of the gap and overlap regions. This sliding of triple helices which are aligned according to the scheme of Hodge and Petruska is coupled with a stretching of the cross-linked telopeptides. This interpretation is supported by calculated axial electron density distributions under consideration of the relative intensities derived from models with varying length of gap and overlap regions, as well as by comparison with model calculations which include telopeptides.

Tension-induced molecular rearrangements in wet native fibres of rat-tail tendons and human finger flexor tendons are registered with the help of time-resolved diffraction spectra using synchrotron radiation. The tension-induced increase of the 67 nm D period is combined with changes in the intensities of some orders of the meridional small angle reflection. Both effects are reversible when unloading the fibre, but are preserved when the load is held constant until the fibre tears. The increase in the D period is partly due to a sliding of the triple helices relative to each other and partly due to a stretching of the triple helices themselves. The sliding of the triple helices results in an alteration of the D stagger, leading to a change in the length of the gap and overlap regions, and to a stretching of the cross-linked telopeptides. This interpretation is supported by comparison with the relative intensities derived from a model with varying length of gap and overlap regions, as well as by comparison with model calculations that include the telopeptides.

The exchange of the structural water of collagen for alcanols was investigated using X -ray diffraction combined with mechanical measurements. The stepwise dehydration with methanol, ethanol or 1-propanol is reflected by the reversible loss of the characteristic equatorial reflexions of native rat tail tendons. The exchange for 1-alcanols in ascending homologous order is characterized by: 1. an increase in the distance between the axes of the triple helices depending on the number of carbon atoms of the alkyl chain, 2. a shortening of the long-spacing of 67 nm characteristic of native collagen and 3. the herewith correlated increase in tension on isometrically measured fibres. The stepwise dehydration with 2-propanol leads first to a loss of the equatorial reflexions that are characteristic of native collagen, then to their reappearance at smaller diffraction angles. The exchange for 2-alcanols in ascending homologous order is characterized by: 1. a splitted equatorial reflexion at 4.1 ± 0 .1 nm, that stays constant up to 2-nonanol, and moves to 4 .8 - 5 .0 ± 0 .1 nm with more than 9 carbon atoms in the alkyl chain, 2. a shortening of the long spacing of 67 nm characteristic of native collagen and 3. the herewith correlated increase in tension on isometrically measured fibres. Stereochemical requirements are discussed as well as consequences for the structural model of collagen.

A method for fitting of background-based curves is described whereas, with it’s aid, the peakpositions and areas in fitted spectrum sought, are easily located

Eine unter Zugbelastung begrenzte Parallelverschieblichkeit sich überlappender Untereinheiten (Fibrillen und Subfibrillen) wird als ein wesentliches Merkmal des Ordnungsprinzips kollagener Fasern angegeben.

A limited glide of overlapping subunits of collagen fibres under stretching forces represents a characteristic feature of the system. The viscoelastic behaviour of human and animal tendon collagen is described simultaneously by mechanical, morphological and X-ray data and correlated with the structural principle of the fibres.

Changes in the large periodic structure of collagen were investigated with the aid of synchrotron radiation. Following results were obtained: 1) Macroscopic extension results in elastic deformation of the elements which are determinant for the structure. 2) The increase of the large period is not proportional to the macroscopic stress. 3) The interpretation of these facts requires a mechanical coupling between the structural units. Up to extensions of 4% this coupling is produced by means of a viscoelastic matrix. 4) In all probability the polypeptide helices are deformed in an inhomogeneous mode. The results were set against measurements on human tendon and on artificially crosslinked collagen. The relations between the mechanical behaviour and the change of the large period were compared with the properties of a mathematical model.

Abstract The content of trace elements in several organs of rats under the influence of D-penicillamine (D-PA) was investigated by the neutronactivation-analysis. It could be shown an diminution of Cu, and Co under D-PA-treatment, the content of Fe, Mn, Rb and Zn was not influenced. The investigat­ ed organs didn’t show any submicroscopic alterations under D-PA. On isolated collagen fibrils of tail tendon was seen a significantly diminuition of E-moduls. In accordance with Siegel the principal effect of D-PA is thought to block the synthesis of functional groups from Schiff-base crosslink precursors but not to inhibit lysyloxidase by loss of Cu-ions of connective tissue. The thermostability of D-PA influenced fibrils is changed in stretched state only and will be due to the lack of crosslink Schiff-bases; where as the shrinking point of not stretched fibrils shows only aging dependent changes.

Banded fibrous associates are described in the extracellular space of connective tissue from human endometrium, Ehlers-Danlos syndrome and of tendon rupture. In the cases of morbus Dupuytren these associates are also found as intracellular inclusions. The banded structures are interpreted as states of an enzymatically induced degradation of collagen in correlation with Type-III collagen.

The affect of stretch on collagen was investigated. Alterations of mechanical dimensions and thermostability of fibrils were measured and changes in fine structure determined by x-ray diffraction and electronmicroscopy.

QuergebÄnderte filamentÄre Assoziate werden im Extrazellularraum des Endometrium, im Bindegewebe eines EDS-Patienten und einer rupturierten Sehne sowie beim Morbus Dupuytren auch intrazellulÄr beschrieben. Diese Assoziate werden als Momentaufnahmen auf dem Wege eines kollagenolytischen Prozesses gedeutet und mit der Anwesenheit von Typ III-Kollagen in Zusammenhang gebracht.