Proteins sedimentation coefficients

Fig. 2. Ultracentrifugal pattern for the water-extractable proteins of defatted soybean meal in pH 7.6, 0.5 ionic strength buffer. Numbers above peaks are approximate sedimentation coefficients in Svedberg units, S. Molecular weight ranges for the fractions are 2S, 8,000—50,000 7S, 100,000—180,000 IIS, 300,000—350,000 and 15S, 600,000—700,000 (9). The 15S fraction is a dimer of the IIS protein (10).

Ribosomes, the supramolecular assemblies where protein synthesis occurs, are about 65% RNA of the ribosomal RNA type. Ribosomal RNA (rRNA) molecules fold into characteristic secondary structures as a consequence of intramolecular hydrogen bond interactions (marginal figure). The different species of rRNA are generally referred to according to their sedimentation coefficients (see the Appendix to Chapter 5), which are a rough measure of their relative size (Table 11.2 and Figure 11.25). 

Properties of Latia luciferase and the purple protein. The absorption spectra of purified Latia luciferase and the purple protein are shown in Fig. 6.1.4. The sedimentation coefficient (sjo) of the... 

Ribosomes are ancient ribonucleoprotein complexes that are the sites of protein synthesis in living cells. Their core structures and fundamental functional mechanisms have been conserved throughout the three domains of life bacteria, archaea and eukaryotes. All ribosomes are organized into two subunits that are defined by their apparent sedimentation coefficient, measured in Svedberg units (S). There is a general... 

The CONSULTATION function is run by using the mouse to select the text "CONSULTATION" from the computer screen. The first question of the dialogue, "Please enter the class of your sample of interest", appears on the screen. The pop-up menu lists the sample types to chose from. The investigator then uses the mouse to select the appropriate response from the pop-up menu. This question and answer procedure continues until SpinPro has enough information, typically 10 to 15 questions, from which to infer all of the relevant parameters. The dialogue is directed by SpinPro in response to answers to previous questions. Thus, if the sample is a protein, SpinPro requests the sedimentation coefficient if the sample is a nucleic acid, SpinPro requests the type of nucleic acid. At the conclusion of the dialogue, the reports are written to the disk. Using the pop-up menu, the reports can be read or saved. 

A summary of the report follows The problem is to separate proteins. Furthermore, SpinPro should pay particular attention to the purity of the separation. The sample is not negatively affected by sucrose, has a sedimentation coefficient of 16 Svedbergs, and is in liquid form of 3 mL and a concentration of 1% w/w. The protein of interest should be placed 45% from the top of the gradient at the end of the run. Of the gradient concentrations 10-40% and 5-20%, the 10-40% is preferred by the investigator. There are no solvents in the sample that are harmful to the tubes. Finally, from the lab, SpinPro should use the L2-75B ultracentrifuge and the SW 41 Ti rotor, which does not require a speed derating due to its age. 

Particle class Protein Separation vs Concentration Separation Optimization criterion Purity Assoc/Dissoc in sucrose No Sedimentation coefficient 16.0 10-40% or 5-20% gradient 10-40 Sample form liquid/semi-solid Total sample volume (mL) 3.0 Sample concentration % w/w 1.0 Selected final location 45.0 Solvents No... 

The term proteasome is used to describe two kinds of multisubunit proteolytic complexes, the 26S and 20S, based on their sedimentation coefficient. The 26S proteasome degrades ubiquitinated protein substrates. The 26S complex contains the 20S as a core and regulatory caps on either end like a dumb bell. Each cap of the 26S proteasome is known as the 19S regulatory complex (19S RC). The 20S core is a cylindrical structure consisting of the catalytic part of the proteasome. ... 

Figure 1.7 Structure of a ribosome. It is composed of two subunits the large 60S subunit has a mass of 2800 kDa and is composed of three RNA molecules and about 50 protein molecules. The smaller AOS subunit contains one RNA molecule plus around 30 protein molecules and has an aggregate mass of 1400 kDa. ( S is an abbreviabon for a Svedberg, the unit of the sedimentation coefficient. This is measured in an analybcal ultracentrifuge and is related to, but not simply proporbonal to, molecular mass.)...

Ribosomes consist of two subunits of different size, made up of ribosomal RNA (rRNA) and neariy 80 proteins (the number of proteins appiies to rat iiver ribosomes), it is customary to give the sedimentation coef cients (see p. 200) of ribosomes and their components instead of their masses. For exampie, the eukaryotic ribosome has a sedimentation coefficient of 80 Svedberg units (80 S), whiie the sedimentation coef cients of its subunits are 40 S and 60 S (S vaiues are not additive). 

Each E. coli cell contains 15,000 or more ribosomes, making up almost a quarter of the dry weight of the cell. Bacterial ribosomes contain about 65% rRNA and 35% protein they have a diameter of about 18 nm and are composed of two unequal subunits with sedimentation coefficients of 30S and 50S and a combined sedimentation coefficient of 70S. Both subunits contain dozens of ribosomal proteins and at least one large rRNA (Table 27-6). 

Sedimentation. The sedimentation experiments are tabulated in Tables I and II. In Table I typical sedimentation coefficients determined in H20 and D20 are in close agreement here and with previously reported values determined for both protio and deuterio phycocyanin from F. calothricoides (15,16). Each of the tabulated coefficients is for a single experiment at an approximate protein concentration of 15 mg. per ml. Lyophilizing a phycocyanin preparation twice had little effect on the observed sedimentation coefficients. In calculating the S values the same partial specific volume of the protein was used for both D20 and H20. This practice is consistent with the recent results of Edelstein and Schach-man (7). Small increases in sedimentation coefficients from H20 to D20 are to be expected because of deuterium substitution on exchangeable positions. The slope of an S vs. concentration plot for phycocyanin in H20 and D20 would also probably differ. Consequently, small changes in S from H20 to D20 would be expected at a constant protein concentration. 

Ribosomes are large complexes of protein and rRNA (Figure 31.8). They consist of two subunits—one large and one small—whose relative sizes are generally given in terms of their sedimentation coefficients, or S (Svedberg) values. [Note Because the S values are determined both by shape as well as molecular mass, their numeric values are not strictly additive. For example, the prokaryotic 50S and 30S ribosomal subunits together form a ribosome with an S value of 70. The eukaryotic 60S and 40S subunits form an 80S ribosome.] Prokaryotic and eukaryotic ribosomes are similar in structure, and serve the same function, namely, as the "factories" in which the synthesis of proteins occurs. 

The ribosomes of Escherichia coli (M = 2.3 x 106 dalton) consist of two dissimilar subunits. The larger one is the 50 S unit containing 32 unique proteins (L1-L34) and one molecule each of 5 S and 23 S rRNA. The smaller subunit has a sedimentation coefficient of 30 S and contains one molecule 16 S rRNA and 21 unique proteins (S1-S21). The proteins of both subunits could be separated by RPC on a C 18 column (250 x 4.6 mm do = 30 nm dP = 10 pm) by a gradient water/2-propanol with 0.1 % trifluoroacetic acid in both solvents (Fig. 20). With 2-propanol, 15 proteins of the... 

The sedimentation coefficient of spleen exonuclease, measured by centrifugation in a sucrose density gradient, using cytochrome c as the reference protein, was 4.6 S 11). The enzyme is eluted from Sephadex G-100 between acid phosphomonoesterase (s = 5.6 S) and acid DNase (s = 3.4 S). 

Chemical composition and sedimentation coefficients (s 0) of proteoglycan monomer fractions from bovine articular cartilage (36). Column 1 shows the amino acid composition of the hyaluronic acid-binding region of proteoglycan monomer core protein, isolated... 

Tanford, C., Kawahara, K. and Lapanje, S. (1967). Proteins as random coils. I. Intrinsic viscosities and sedimentation coefficients in concentrated guanidine hydrochloride. Journal of the American Chemical Society, 89, 729-736. 

Lovenberg, Buchanan, and Rabinowitz 65) showed that the molecular weight of C. pasteurianum ferredoxin is about 6000, based on sedimentation velocity and sedimentation equilibrium ultracentrifugation determinations and on amino acid analysis. The sedimentation coefficient, S2o,w was 1.4, and the partial specific volume, determined according to the method of Hvidt et al. 59) was 0.63, as compared to the value of 0.71 observed for most proteins. Similar investigations showed that ferredoxins from four other clostridia Lovenberg, Buchanan, and Rabinowitz 65)) and from a photosynthetic bacterium (Bachofen and Arnon 12)) also had a molecular weight of about 6000. 

The sedimentation coefficient is often reported in Svedberg units, S, named in honor of The Svedberg, the inventor of the ultracentrifuge 1 S = 10 13 seconds. Sedimentation coefficients of some selected proteins are listed below. 

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