R. Jonak

Topochemistry of the binding of phosphotungstic acid to collagen.

Abstract The interaction between collagen and phosphotungstic acid can be divided into two specific reaction steps, dependent on the steric arrangement. 1. (1) A relatively quick, firm intersubfibrillar binding (within ≈ 10 min) of the polyanions PW 12 O 40 3− to easily accessible basic groups. This occurs even when the units become more compact through tension, as indicated by meridional layer-line reflections. 2. (2) A less tight, intrasubfibrillar bond to relaxed incubated fibres (≧ 20 min) with participation of relatively heavy accessible amino groups, indicated by an equatorial reflection at ~19 A. The intrasubfibrillar PW 12 O 40 3− deposition is restricted by previous aldehyde cross-linking of the fibres, whereas it continues further with non-drawn and non-crosslinked fibres. In the latter case, a contraction of the fibre and a shortening of the 670 A period are observed. The polyanion PW 11 O 39 7− present at pH 5.5 to 7 is evidently bound to relaxed fibres by the guanido group only. The scattering reflections, the contraction of phosphotungstic acid-treated fibres and the associated changes of the long period, are interpreted on the basis of an eight-stranded unit for the subfibrils. These results have been obtained with native and chemically modified collagen fibres using conventional and synchrotron X-ray radiation as well as mechanical measuring devices.

Die Viskoelastizität parallelsträngigen Bindegewebes und ihre Bedeutung für die Funktion

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. The existence of gliding subunits is proven by retardation- and relaxation-experiments in combination with short-time-x-ray-measurements by synchrotron-radiation. This behaviour may explain the damping properties of tendons. The retractive force of deformed helical and nonhelical molecular chains is generally thought to be responsible for the elasticity of the system. Length-increase of tendons during growth may be also correlated with the gliding processes. The so called conditioning-effect is due to an improved arrangement of possible reacting groups by cyclic stretch which can be well demonstrated on low ordered samples and is therefore greater in the case of juvenile specimens than in older ones. A quick first stretch causes greater molecular deformations than further stretches of the same strength, and may lead to disordered domains in the structure. A mathematical model for the simulation of the mechanical properties is given and was used for the calculation of some examples. Eine unter Zugbelastung begrenzte Parallelverschieblichkeit sich überlappender Untereinheiten (Fibrillen und Subfibrillen) wird als ein wesentliches Merkmal des Ordnungsprinzips kollagener Fasern angegeben. Das viskoelastische Verhalten von menschlichem und tierischem Sehnenkollagen wird anhand kombinierter mechanischer, röntgenographischer und morphologischer Meßdaten beschrieben und mit dem Ordnungsprinzip der Fasern korreliert. Das Vorliegen parallel verschieblicher Untereinheiten wird durch Retardations- und Relaxationsversuche in Kombination mit Kurzzeitbeugungsmessungen unter Einsatz der Synchrotronstrahlung bewiesen und mit der dämpfenden Eigenschaft der Sehnenfasern in Zusammenhang gebracht. Für die elastische Eigenschaft der Sehnenfasern wird die Rückstellkraft deformierter helikaler und nichthelikaler Molekülketten verantwortlich gemacht. Das Längenwachstum von Sehnenfasern wird mit dem Gleitvermögen von Untereinheiten korreliert. Der auf eine Verbesserung der Zueinanderausrichtung potentieller Bindungspartner beruhende Konditionierungseffekt einer zyklischen Faserbelastung ist an weniger gut formierten Einheiten besonders auffällig und entsprechend an jugendlichen Sehnenfasern größer als an alten. Die stoßartige Belastung einer Sehnenfaser aus der Ruhephase führt zu größeren molekularen Deformationen als nachfolgende gleichhohe Belastungen und kann fibrilläre Gefügestörungen hervorrufen. Es wird eine Modellkonstruktion zur Simulation mechanischer Eigenschaften von Kollagen beschrieben und für einige Beispiele durchgerechnet.

Glutaraldehyde-induced states of stress of the collagen triple helix

Abstract Demonstration of a decrease in pitch of some turns of the collagen triple helix caused by glutaraldehyde as shown in the stress and low-angle X-ray diagram by use of synchrotron radiation.

The elasticity of the collagen triple helix

Fig. i. Meridional x-ray reflections from a 22month-old RTT fiber ( ~ 0.09 mm2; strain 7 %). The spectrum was recorded by a positionsensitive detector with a xenon-methane mixture as chamber gas. Time of exposition 100 s; max. peak height 1655 pulses. In order to exclude disturbing scattering a large zone around the primary beam was masked. The distance of the peaks of the 9th order comes to 395 channels. This being so, the resolution is approximately the width of one channel, and one can minimally detect a change of 0.25%. The low-angle spacing amounts to 685 +1 •. After discharge it was reduced again to the starting value of 670 A 1. The 670-A low-angle spacing is due to secondary units which will not be influenced in the lower part (strain < 3%), because, 2. the intermolecular cross-links out of peptide chains will be elongated in such a way that the secondary units can slip reversibly [3]. 3. In th e upper linear part (strain > 3%) the force is applied to the secondary units and now the triple helix itself becomes elongated elastically, so that the low-angle spacing increases reversibly by 2-3%. A detailed communication will be published elsewhere.

Knickdeformationen an Kollagen

SummaryThe 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.Collagen underwent changes both in tensile strength and fine structure following stretch beyond the physiological range. The severity of these changes depended both on the degree of stretch and the cross-link density of the collagen. Fibrils either became split into bundles consisting of subfibrillar units or showed circumscribed kinking deformities. The mechanism producing kinking was investigated. It is possible that a connection exists between fibrillar kinking and tendon rupture.ZusammenfassungExperimentelle Untersuchungen zeigen, daß überdehntes Kollagen Änderungen seiner Zugfestigkeit und seines Ordnungszustandes erfährt. Je nach Belastung und Vernetzungsgrad zeigen die nach Dehnung entspannten Fibrillen Aufspleißungen in mehr oder weniger einheitliche Bündel aus Subfibrillen oder umschriebene Abknickungen. Der Mechanismus der Knickdeformationen wird analysiert. Auf einen möglichen Zusammenhang zwischen Knickdeformation und Sehnenruptur wird hingewiesen.Die Untersuchungsergebnisse werden belegt durch die Bestimmung mechanischer Größen und der Thermostabilität der Proben sowie ihres Ordnungszustandes mit Hilfe der Röntgenbeugung und Elektronenmikroskopie.

Über die Bestimmung von Langperioden-Änderungen am Kollagen/ On the Determination of Changes in the Large Periodic Structure of Collagen

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.

Fibrilläre Gefügestörung bei Sehnenruptur

Areas of disordered fibrillar structure similar to kinking deformities have been observed in specimens from ruptured tendons. It seems possible to compare this phenomenon with experimentally produced deformations. The significance for the pathomechanics of tendon rupture is discussed.SummaryAreas of disordered fibrillar structure similar to kinking deformities have been observed in specimens from ruptured tendons. It seems possible to compare this phenomenon with experimentally produced deformations. The significance for the pathomechanics of tendon rupture is discussed.ZusammenfassungIn Exzisaten aus dem Rupturbereich von Sehnen wurden fibrilläre Gefügestörungen in der Art von Knickdeformationen beobachtet, die einen Vergleich mit Deformationen in experimentell überdehnten und entspannten Kollagenfasern zulassen. Auf die mögliche Bedeutung für die Pathomechanik der Sehnenruptur wird hingewiesen.

Der Einfluß von D-Penicillamin auf den Gehalt einiger Organe an Spurenelementen sowie auf die mechanischen Eigenschaften von Kollagen / Trace Elements in Several Organs and Mechanical Properties of Collagen under the Influence of D-Penicillamin

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.