Maximum-entropy calculation of the electron density at 4 A resolution of Pf1 filamentous bacteriophage.

A 4 A electron-density map of Pf1 filamentous bacterial virus has been calculated from x-ray fiber diffraction data by using the maximum-entropy method. This method produces a map that is free of features due to noise in the data and enables incomplete isomorphous-derivative phase information to be supplemented by information about the nature of the solution. The map shows gently curved (banana-shaped) rods of density about 70 A long, oriented roughly parallel to the virion axis but slewing by about 1/6th turn while running from a radius of 28 A to one of 13 A. Within these rods, there is a helical periodicity with a pitch of 5 to 6 A. We interpret these rods to be the helical subunits of the virion. The position of strongly diffracted intensity on the x-ray fiber pattern shows that the basic helix of the virion is right handed and that neighboring nearly parallel protein helices cross one another in an unusual negative sense

Quantitative analysis of the molecular sliding mechanisms in native tendon collagen — time-resolved dynamic studies using synchrotron radiation

The stretching of native fibres from rat tail tendons (RTT) was monitored in time-resolved X-ray measurements using synchotron radiation, by registering one meridional small angle diffraction pattern every second. The time course of this dynamic molecular process was analyzed quantitatively with the help of model calculations based on the amino acid sequence. The results show that two mechanisms contribute to the elongation of fibrils, namely the stretching of the collagen triple helices and their sliding relative to each other (increase of the D stagger). The results further show that these two processes do not take place simultaneously. The first increase of the D period from 67.0 nm to about 67.6 nm is correlated with a stretching of the triple helices. The further increase of the D period is due to a continuous increase of the D stagger. This succession is independent of the age of the animals and also independent of the stretching velocity. The stretching process is shown to be reversible at the molecular level up to a D period of about 68.4 nm

Structural dynamic of native tendon collagen

The dynamic behaviour of collagen fibrils is revealed by time-resolved X-ray investigations of native rat tail tendon fibres in tensile tests

Maximum-entropy calculation of the electron density at 4 Å resolution of Pf1 filamentous bacteriophage

A 4 Å electron-density map of Pf1 filamentous bacterial virus has been calculated from x-ray fiber diffraction data by using the maximum-entropy method. This method produces a map that is free of features due to noise in the data and enables incomplete isomorphous-derivative phase information to be supplemented by information about the nature of the solution. The map shows gently curved (banana-shaped) rods of density about 70 Å long, oriented roughly parallel to the virion axis but slewing by about 1/6th turn while running from a radius of 28 Å to one of 13 Å. Within these rods, there is a helical periodicity with a pitch of 5 to 6 Å. We interpret these rods to be the helical subunits of the virion. The position of strongly diffracted intensity on the x-ray fiber pattern shows that the basic helix of the virion is right handed and that neighboring nearly parallel protein helices cross one another in an unusual negative sense