Protein diameter

Fig. 4.4 Pore-filling models for protein adsorption in a mesopore channel (a) separated single-molecularadsorption (b) separated double-molecular adsorption (c) separated triple-molecular adsorption (d) interdigitated triple-molecular adsorption where adjacent layers are interdigitated by 1/4 of the protein diameter through changing the relative orientation. Adapted from [37],...

An alternative description of protein-containing RMs was given by Levashov et al. [148] from ultra-centrifugation studies. Water-soluble dyes (picric acid) were used to determine the molecular weights and sedimentation behavior of the non-protein-containing and protein-containing RMs. The proposed model involved two regimes of Wg (i) at low Wg (where the inner reverse micellar diameter was less than the protein diameter), the protein created a new RM around itself such that the volume of the inner cavity of the filled RM was essentially the volume of the solubihzed protein and (ii) at water contents where... 

With low linear-energy-transfer (LET) particles such as electrons, gamma, or X rays of about 1 MeV, ionizations or hits occur at a distance greater than 100 nm from each other. This distance is larger than protein diameters (about 4 to 15 nm) so that ionizations occur completely at random in the protein sample. The statistical Poisson distribution for the probability of no hit, T(0), is applied for such independent events and expressed in a simplified form as... 

Controlled pore glass (CPG) has application as media for size exclusion and afQnity chromatographic media, commonly used to separate proteins. Nominally, the pore diameter should be 10 times the protein diameter. Most proteins [51] have a diameter below 3 nm. CPGs are required to have sharp, unimodal pore distributions, that is a high volume of pores of similar size. Clearly, a means of investigating pore size, pore... 

Interactions between like-charged proteins at 25 C. The protein diameter is 0.4 nm. To the left, an ionic strength of 0.28 M and salts containing monovalent cations. Tothe rightdivalentcationsat0.31 M. Thedashed line in the figure is not of relevance In this discussion. Reprinted from Prausnitz (2003), with permission from Elsevier. 

Silk (qv) suture is made from the threads spun by the silkworm Bombjx mori. The fiber is composed principally of the protein fibroin and has a natural coating composed of sericin gum. The gum is usually removed before braiding the silk yams to make sutures in a range of sizes. Fine silk sutures may be made by simply twisting the gum-coated silk yams to produce the desired diameter. White silk is undyed. Silk is either dyed black with logwood extract or blue with D C Blue No. 9. The suture may be uncoated or coated either with high molecular weight polydimethylsiloxane or with wax. 

The number of helical turns in these structures is larger than those found so far in two-sheet p helices. The pectate lyase p helix consists of seven complete turns and is 34 A long and 17-27 A in diameter (Figure 5.30) while the p-helix part of the bacteriophage P22 tailspike protein has 13 complete turns. Both these proteins have other stmctural elements in addition to the P-helix moiety. The complete tailspike protein contains three intertwined, identical subunits each with the three-sheet p helix and is about 200 A long and 60 A wide. Six of these trimers are attached to each phage at the base of the icosahedral capsid. 

Very few self-sufficient viruses have only 60 protein chains in their shells. The satellite viruses do not themselves encode all of the functions required for their replication and are therefore not self-sufficient. The first satellite virus to be discovered, satellite tobacco necrosis virus, which is also one of the smallest known with a diameter of 180 A, has a protein shell of 60 subunits. This virus cannot replicate on its own inside a tobacco cell but needs a helper virus, tobacco necrosis virus, to supply the functions it does not encode. The RNA genome of the satellite virus has only 1120 nucleotides, which code for the viral coat protein of 195 amino acids but no other protein. With this minimal genome the satellite viruses are obligate parasites of the viruses that parasitize cells. 

Figure 18.3 Protein crystals contain large channels and holes filled with solvent molecules, as shown in this diagram of the molecular packing in crystals of the enzyme glycolate oxidase. The subunits (colored disks) form octamers of molecular weight around 300 kDa, with a hole in the middle of each of about 15 A diameter. Between the molecules there are channels (white) of around 70 A diameter through the crystal. (Courtesy of Ylva Lindqvist, who determined the structure of this enzyme to 2.0 A resolution in the laboratory of Carl Branden, Uppsala.)...

Sephadex type Grade Dry bead diameter (/urn) Fractionation range peptides and proteins (g/mol) Fractionation range dextrans (g/mol) Swelling factor (ml/g dry Sephadex) Maximum operating pressure" (cm H,0) Permeability Ko Maximum linear velocity" (cm/hr) Swelling time (h) ... 

Type diameter (/tm) Proteins (M,) Dextrans (M,) operating pressure (kPa) pH stability... 

FIGURE 7.13 Preparative separation of various proteins on Fractogel EMD BioSEC (S). The length of the column was 1000 mm and the inner diameter 100 mm. The flow rate was 6.2 ml/min with 20 sodium phosphate buffer (pH 7.2) containing 0.3 M NaCI as the eluent. The injected standard proteins can be used to create a calibration curve. 

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