Infrared spectra of E. coli ribosomes, and of extracted RNA and ribosomal proteins have been determined. From the spectra of stacked, single-stranded homopolyribonucleotides it is shown that the spectrum of a polynucleotide chain is essentially a function of the extent of base-pairing, and is only to a small extent affected by stacking. It is shown that the spectrum of the intact ribosome is the linear sum of contributions from native RNA (about 60% base-paired) and protein. It can not be expressed in terms of unpaired RNA. It is thus clear that the conformation of the RNA in the ribosome is, at least in terms of the extent of base-pairing, very similar to that of free RNA in solution. The spectra of the whole ribosomal proteins have been examined in acid and in neutral solution; for the latter the procedure of Traub and Nomura was followed, as for preparation of the proteins for recombination with RNA to produce native subunits. In this state the infrared spectrum shows the proteins to be predominantly in the β-conformation. It is suggested that the concept of a native structure for the ribosomal proteins is meaningful only in their native environment on the RNA. Parallels with histones and nucleohistones are noted.
Abstract The theme is scientific foible. Gratzer describes for a general readership a number of episodes in science and medicine where an erroneous research finding was adhered to and given credence by its originators and others far beyond the point where it had been effectively discredited. Each of these episodes is dealt with in detail, with special attention given to the individuals involved, their careers and personalities, their relations with others, and so on. A fascinating, well written collection of stories from the history of science. They include the affair of the N-rays ('the best and most widely analysed example of tribal delusion in the history of science'), Lysenko and the tragedy of Soviet genetics, science in the Third Reich, the tale of polywater, and the cold-fusion aberration of the 1980s. The writing is very clear and eminently readable with good use made of anecdotes and literary references. Here is a book that is both entertaining and thought-provoking.
Changes induced on addition of the cofactor, NAD, to glyceraldehyde-3-phosphate dehydrogenase from yeast have been investigated by hydrodynamic and spectroscopic techniques. As shown by light-scattering and sedimentation and diffusion studies, the tetrameric structure of the holoenzyme persists under all but strong dissociating conditions: there is thus no change in the quaternary structure on binding. On the other hand, binding is accompanied by an increase of some 4% in the sedimentation coefficient, which is too large to be explicable in terms of the increase in particle weight by bound ligand. A conformational change is also observed by optical rotatory dispersion and circular dichroism measurements. The magnitude of the Cotton effect associated with the aromatic chromophores of the protein, near 280 nm, increases, whereas the rotation in the neighbourhood of 233 nm undergoes a small diminution as the cofactor is added. It is shown that these changes are conformational in origin, rather than a consequence of NAD attachment per se. Increasing the temperature in the range 20–40° leads to a transition from non-cooperative to cooperative binding of NAD to the apoenzyme. At 40°, where NAD binding is weakly sigmoidal, the change in optical rotation is likewise sigmoidal and parallels the increase in the sedimentation coefficient. At 20° both the uptake of NAD and the structural changes are hyperbolic. In the cooperative situation the data are shown to be consistent with the two-state “concerted” model for ligand-binding and incompatible with a sequential mechanism.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(72 0 0)'/%3e%3cuse xlink:href='%23a' transform='rotate(-72 0 0)'/%3e%3cuse xlink:href='%23a' transform='scale(-1 1) rotate(72)'/%3e%3c/g%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h1200v600H0z'/%3e%3cpath stroke='%23FFF' stroke-width='60' d='m0 0 600 300M0 300 600 0' clip-path='url(%23b)'/%3e%3cpath stroke='%23C8102E' stroke-width='40' d='m0 0 600 300M0 300 600 0' clip-path='url(%23c)'/%3e%3cpath stroke='%23FFF' stroke-width='100' d='M300 0v300M0 150h600' clip-path='url(%23b)'/%3e%3cpath stroke='%23C8102E' stroke-width='60' d='M300 0v300M0 150h600' clip-path='url(%23b)'/%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='matrix(45.4 0 0 45.4 900 120)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='matrix(30 0 0 30 900 120)'/%3e%3cg transform='rotate(82 900 240)'%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='rotate(-82 519.022 -457.666) scale(40.4)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='rotate(-82 519.022 -457.666) scale(25)'/%3e%3c/g%3e%3cg transform='rotate(82 900 240)'%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='rotate(-82 668.57 -327.666) scale(45.4)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='rotate(-82 668.57 -327.666) scale(30)'/%3e%3c/g%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='matrix(50.4 0 0 50.4 900 480)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='matrix(35 0 0 35 900 480)'/%3e%3c/svg%3e)