W. Hoppe

Three-dimensional reconstruction and averaging of 30 S ribosomal subunits of Escherichia coli from electron micrographs.

From the micrographs of a tilt series, several particles of negatively stained 30 S ribosomal subunits of Escherichia coli were three-dimensionally reconstructed. Three of them showing similar orientation with respect to the supporting foil were averaged after alignment by newly developed three-dimensional correlation methods. As a main result we found a stained channel-like structure inside the particle. We tentatively propose that this corresponds, at least partially, to positively stained segments of the 16 S RNA.

Trace structure analysis, ptychography, phase tomography

Abstract Three papers dedicated to the author elicit further comment stemming from his own engagement with the three topics- trace structure analysis, ptychography and phase tomography.

Electron microscopy of thin protein crystal sections

Abstract In continuation of an earlier publication (Hoppe et al. , 1968), further experiments are described here on the preparation of thin film sections of embedded protein crystals for investigation by electron microscopy and electron diffraction. Several embedding media were compared, the best being Aquon. Periodicities were observed in electron micrographs as well as in electron diffraction patterns. In diffraction experiments the best resolution observed was approximately 10 to 11 A.

Zur elektronenmikroskopisch dreidimensionalen Rekonstruktion eines Objektes

u einiger Zeit wurde die Rekonstruktion der Struktur eines dre.idimensionalen Objektes aus einer Anzahl yon gegeneinander verschwenkten elektronenmikroskopischen Aufnahmen vorgeschlagen [ t --3] . Die Fouriertransformierten-Theorie der Rekonstruktion wurde in [4] entwickelt. Eine im Prinzip v611ig analoge Ableitung enth~ilt auch [5]. Inzwischen hat es sich herausgestellt, dal3 das Problem der dreidimensionalen Rekonstruktion aus Projektionen schon vor den elektronenmikroskopischen Arbeiten ftir die Radiologie (Bestimmung des Modells eines menschlichen KSrpers aus R6ntgendurchstrahlungen) und die Radioastronomie bearbeitet worden war. Auf die entsprechenden mathematischen Arbeiten die meist die unmittelbare Rekonstruktion im Ortsraum zum Ziele hatten kann in diesem Zusammenhang nicht eingegangen werden.

Experimental test of a new method for phase determination using gamma resonance spectroscopy

We have performed an experimental study of the feasability to employ resonance scattering of γ-radiation in order to measure directly the phase of the structure factor which is required in X-ray crystal structure determination. The phases of the (020) and the (040) reflection of a K3Fe(CN)6 single crystal were determined by measuring the interference between nuclear resonance scattering and by electronic scattering.

Unit cell and space group of catalase from Micrococcus luteus.

Octahedral shaped crystals of about 1 mm were grown from catalase of Micrococcus luteus. The space group was determined as P422121 with a = b = 106.6 A and c = 106.3 A. In contrast to mammalian catalase, the bacterial catalase contains only one subunit per asymmetric unit. This proves that the four subunits of bacterial catalase are identical.

X-ray structure analysis of 5-anilinopentadienylidenanilinium bromide, C17H17BrN2

The crystal and molecular structure of 5-anilinopentadienylidenanilinium bromide has been solved by X-ray diffraction methods. The crystals of this compound are monoclinic, space groupC2/c (No. 15), with unit cell data:a = 14.63,b = 12.68,c= 17.77 Å and β = 104.8 °,Dm = 1.39 g cm−3,Z = 8,Dc = 1.37 g cm−3 and μ = 38.4 cm−1 (CuKα radiation). The structure has been refined to anR-value of 0.049, using diffractometer intensity data for 2014 reflexions. The bond angles in the pentamethene chain are widened by about 3.8 ° from the expected value of 120 °, owing to the repulsion of hydrogen atoms in the chain. Steric hindrances from the hydrogen atoms cause the phenyl rings to be twisted by approximately 20.7 and 16.5 ° in the opposite directions with respect to the pentamethene chain. The nitrogen atoms take part in hydrogen bonds with the neighbouring bromine atoms (N ...; Br = 3.35 Å).

Physikalische Methoden zur Bestimmung der strukturellen Eigenschaften von Biomolekülen

Proteine und Nucleinsauren bilden Makromolekule, mit Dimensionen bis zu einigen 102 nm und Molekulargewichten bis 108. Zur Bestimmung ihrer (idealisierten) Form, ihrer Grose und ihres Molekulargewichts eignen sich besonders diejenigen physikalischen Methoden, die fur die Analytik synthetischer Makromolekule entwickelt worden sind. Synthetische Polymere fallen aber im allgemeinen nicht mit einem einheitlichen Molekulargewicht M an, sondern mit einer mehr oder weniger breiten Molekulargewichtsverteilung. Fur eine Mischung solcher Makromolekule sei N i die Zahl der Teilchen mit dem Molekulargewicht M i .