Spectrophotometric and turbidimetric methods for measuring proteins
TL;DR: The turbidity produced when protein is mixed with low concentrations of any of the common protein precipitants can be used as an index of protein concentration, and this advantage is used to eliminate the interference of nucleic acids in the estimation of protein.
Abstract: Publisher Summary The turbidity produced when protein is mixed with low concentrations of any of the common protein precipitants can be used as an index of protein concentration. The resulting turbidity is maximum after about 10 minutes and may be measured spectrophotometrically in the wavelength region of 600 m. Standardization may be effected by comparison with the turbidity produced by a suspension of a dried protein precipitate, or reference may be had to the methyl acrylate-styrene polymer. Turbidimetric techniques are rapid and convenient, but they yield different values with different proteins. They do not permit differentiation between protein and acid-insoluble compounds such as nucleic acids. Protein estimation with the Folin-Ciocalteu reagent include (1) biuret reaction of protein with copper ion in alkali, and (2) reduction of the phosphomolybdic-phosphotungstic reagent by the tyrosine and tryptophan present in the treated protein. Protein estimation by ultraviolet absorption takes advantage of the fact that nucleic acid, however, absorbs much more strongly at 260 mμ than at 280 mμ, whereas with protein the reverse is true. This advantage is used to eliminate, by calculation, the interference of nucleic acids in the estimation of protein.
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TL;DR: The 39,500-dalton major outer membrane protein is a serogroup antigen of C. trachomatis organisms and its extraction resulted in a concomitant loss of the COMC membrane structure and morphology.
Abstract: Elementary bodies (EB) of Chlamydia trachomatis serotypes C, E, and L2 were extrinsically radioiodinated, and whole-cell lysates of these serotypes were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Autoradiography of the polypeptide profiles identified a major surface protein with an apparent subunit molecular weight of 39,500 that was common to each C. trachomatis serotype. The abilities of nonionic (Triton X-100), dipolar ionic (Zwittergent TM-314), mild (sodium deoxycholate and sodium N-lauroyl sarcosine), and strongly anionic (SDS) detergents to extract this protein from intact EB of the L2 serotype were investigated by SDS-PAGE analysis of the soluble and insoluble fractions obtained after each detergent treatment. Only SDS readily extracted this protein from intact EB. Sarkosyl treatment selectively solubilized the majority of other EB proteins, leaving the 39,500-dalton protein associated with the Sarkosyl-insoluble fraction. Ultrastructural studies of the Sarkosyl-insoluble EB pellet showed it to consist of empty EB particles possessing an apparently intact outer membrane. No structural evidence for a peptidoglycan-like cell wall was found. Morphologically these chlamydial outer membrane complexes (COMC) resembled intact chlamydial EB outer membranes. The 39,500-dalton outer membrane protein was quantitatively extracted from COMC by treating them with 2% SDS at 60 degrees C. This protein accounted for 61% of the total COMC-associated protein, and its extraction resulted in a concomitant loss of the COMC membrane structure and morphology. The soluble extract obtained from SDS-treated COMC was adsorbed to a hydroxylapatite column and eluted with a linear sodium phosphate gradient. The 39,500-dalton protein was eluted from the column as a single peak at a phosphate concentration of approximately 0.3 M. The eluted protein was nearly homogeneous by SDS-PAGE and appeared free of contaminating carbohydrate, glycolipid, and nucleic acid. Hyperimmune mouse antiserum prepared against the 39,500-dalton protein from serotype L2 reacted with C. trachomatis serotypes Ba, E, D, K, L1, L2, and L3 by indirect immunofluorescence with EB but failed to react with serotypes A, B, C, F, G, H, I, and J, with the C. trachomatis mouse pneumonitis strain, or with the C. psittaci feline pneumonitis, guinea pig inclusion conjunctivitis, or 6BC strains. Thus, the 39,500-dalton major outer membrane protein is a serogroup antigen of C. trachomatis organisms.
1,075 citations
TL;DR: The results suggest that MSN2 and MSN4 encode a DNA‐binding component of the stress responsive system and it is likely that they act as positive transcription factors.
Abstract: The MSN2 and MSN4 genes encode homologous and functionally redundant Cys2His2 zinc finger proteins. A disruption of both MSN2 and MSN4 genes results in a higher sensitivity to different stresses, including carbon source starvation, heat shock and severe osmotic and oxidative stresses. We show that MSN2 and MSN4 are required for activation of several yeast genes such as CTT1, DDR2 and HSP12, whose induction is mediated through stress-response elements (STREs). Msn2p and Msn4p are important factors for the stress-induced activation of STRE dependent promoters and bind specifically to STRE-containing oligonucleotides. Our results suggest that MSN2 and MSN4 encode a DNA-binding component of the stress responsive system and it is likely that they act as positive transcription factors.
1,060 citations
TL;DR: The specificity of the interaction was investigated using a competitive binding assay to compare directly the affinities of various proteins and synthetic polymers for the tannin obtained from Sorghum bicolor (Lin.) Moench, indicating that this proanthocyanidin interacts quite selectively with protein and protein-like polymers.
978 citations
TL;DR: Rat liver was homogenized in isotonic buffer, fractionated by differential centrifugation, and then subfractionated by equilibrium sedimentation in Nycodenz gradients to indicate that the cytosolic and the intermembrane space Cu,Zn-SODs are coded for by the same gene.
967 citations
TL;DR: MCF-7 cells of human breast cancer origin responded to estradiol (E) treatment with increased levels of progesterone receptor (PgR) showing that human breast cells which have undergone malignant changes can continue to synthesize a specific protein under hormone control.
777 citations
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Journal Article•
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
289,852 citations
TL;DR: An investigation of the biochemical changes following experimental liver injury felt the need of a simple, rapid, and accurate method for determining the protein fractions in small amounts of serum and began with Kingsley’s biuret procedure.
15,717 citations
TL;DR: In this article, the authors summarized research into the existing methods for the quantitative determination of tyrosine and tryptophane in proteins, including the Folin-Looney method, which is based on reaction of a phosphotungstic phosphomolybdic acid in a phenol solution.
2,527 citations
1,591 citations