Biomaterial Database

Cryo-electron microscopy of helical particles TMV and T4 polyheads. 1985

J Lepault

Vitrified Tobacco Mosaic Virus (TMV) and T4 polyhead suspensions have been studied by cryo-electron microscopy. The order of TMV particles is preserved to distances better than 0.3 nm when vitrified. In spite of the high beam sensitivity of unstained biological material, the resolution of images extends to 1.15 nm. Radial density distributions calculated from images of TMV and the helical aggregate of TMV protein (TMVP) show that the RNA is likely visualized in the virus. However, due to the imaging conditions of unstained vitrified specimens, the position of the RNA is erroneous. While TMV and TMVP do not show any departure from cylindrical symmetry, T4 polyheads are sensitive to the thickness of the ice layer in which they are embedded. To avoid flattening, T4 polyheads have to be embedded in an ice layer thicker than their diameter.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D008867	Microtomy	The technique of using a microtome to cut thin or ultrathin sections of tissues embedded in a supporting substance. The microtome is an instrument that hold a steel, glass or diamond knife in clamps at an angle to the blocks of prepared tissues, which it cuts in sections of equal thickness.	Thin Sectioning,Ultramicrotomy,Sectioning, Thin,Sectionings, Thin,Thin Sectionings
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D005615	Freezing	Liquids transforming into solids by the removal of heat.	Melting
D012367	RNA, Viral	Ribonucleic acid that makes up the genetic material of viruses.	Viral RNA
D013604	T-Phages	A series of 7 virulent phages which infect E. coli. The T-even phages T2, T4; (BACTERIOPHAGE T4), and T6, and the phage T5 are called "autonomously virulent" because they cause cessation of all bacterial metabolism on infection. Phages T1, T3; (BACTERIOPHAGE T3), and T7; (BACTERIOPHAGE T7) are called "dependent virulent" because they depend on continued bacterial metabolism during the lytic cycle. The T-even phages contain 5-hydroxymethylcytosine in place of ordinary cytosine in their DNA.	Bacteriophages T,Coliphages T,Phages T,T Phages,T-Phage
D014027	Tobacco Mosaic Virus	The type species of TOBAMOVIRUS which causes mosaic disease of NICOTIANA. Transmission occurs by mechanical inoculation.	Mosaic Virus, Tobacco,Mosaic Viruses, Tobacco,Tobacco Mosaic Viruses,Virus, Tobacco Mosaic,Viruses, Tobacco Mosaic
D014764	Viral Proteins	Proteins found in any species of virus.	Gene Products, Viral,Viral Gene Products,Viral Gene Proteins,Viral Protein,Protein, Viral,Proteins, Viral