A simple ultraviolet spectrophotometric method for the determination of protein.

Publisher Summary This chapter discusses the chemical analysis of microbial cells. The preparation of material for analysis is discussed, because changes in the chemical composition of cells may occur as a result of the washing and storage conditions used. Wet- and dry-weight determinations of bacterial samples and assay of total cell numbers are described, because analytical results must refer to one or other of these values. Selection of an analytical procedure is a subjective process, because the number of suitable methods is large and each will have different merits and defects. Primary considerations are sensitivity, specificity, reproducibility, and absolute accuracy. Automatic methods for performing biochemical analyses, already widely accepted in hospitals and in industry, are beginning to make their way into the research laboratory. All automatic analyzers developed so far may be classified as either “continuous-flow” or “discrete” types. All of them use colorimetric methods exclusively and contain some form of automatic colorimeter for final read-out. The first and best-known is the Technicon “AutoAnalyzer,” which is of the continuous-flow type.

Chapter III Chemical Analysis of Microbial Cells

Publisher Summary This chapter deals with the absorption spectra of proteins and amino acids The colored proteins are conjugated proteins in which the protein carrier is colorless This transparency of protein solutions extends into the ultraviolet region of the spectrum and many proteins do not absorb radiation of longer wavelength than 2500 Ǻ The essential protein fabric, consisting of a peptide chain in various forms, is not responsible for absorption at longer wavelengths In case of fibrous proteins, there is some evidence that the peptide fabric is responsible for absorption in this region Many proteins absorb in this region This absorption is due to the aromatic amino-acids present in the protein The advent of quantitative methods of spectrophotometry is the basis of a method of determining tyrosine and tryptophan in proteins The striking property of proteins is their transparency, indicating a high degree of electronic saturation The configurational stability of the protein molecule depends entirely on extra-valence forces and not on unsaturation, which would result in high absorption in the ultraviolet The absence of such rigidifying bonds endows the protein with its unique characters of plasticity, while the number-sequence of side chains gives its chemical constancy These two properties allow these molecules to be arranged in large polymorphic masses to form a matrix fabric of recurrent pattern in media, which are essentially aqueous The material reviewed is principally derived from the study of homogeneous absorbing systems, in which the inhomogeneity is finer in grade by several orders than the dimensions of the exploring light beam

Ultraviolet absorption spectra of proteins and amino acids.

Publisher Summary This chapter reviews that the simplest way of accounting for the absorption spectrum of a protein is as the sum of the spectra of its components. This gives results which are often good approximations to the observed protein spectrum. The assumption of additivity is basic for useful analytical applications of spectral measurements. It discusses that in another perspective, the failure of perfect additivity of the component absorptivities affords the possibility of obtaining structural information about proteins. The absorptivity of the peptide bond can change by as much as a factor of two with a change in the conformation of a peptide chain. Since the absorptivity of aromatic side chains is much less sensitive to environmental change, correspondingly, more sensitive techniques are required to measure the small changes which do occur. The nature and limitations of the structural information resulting from both peptide-bond and side-chain absorption are discussed. Absorption spectra can occasionally be a useful tool in the identification of unusual structural features in proteins and polypeptides. Several such applications are also explained in this chapter.

Ultraviolet spectra Of Proteins and Amino Acids

Superoxide Dismutase: ORGANELLE SPECIFICITY

The ultraviolet absorption spectra of proteins

The absorption spectra of amino acids in the region two hundred to two hundred and thirty millimicrons.

Scanning electron microscopy in conjunction with cell isolation procedures revealed details of the packing of threads in hagfish slime gland thread cells. Biochemical studies indicate that the thread is largely composed of a protein subunit with a molecular weight of 63,500. Mathematical calculations suggest that the thread may attain lengths of 60 centimeters or more.

https://science.sciencemag.org/content/sci/212/4492/326.full.pdf

Threads in the hagfish slime gland thread cells: organization, biochemical features, and length.

The absorption spectra of proteins have been made the subject of considerable study. For the greatest number of proteins there has been demonstrated a broad band with a peak at about 280 rnp and a minimum, on the short wave-length side, at about 250 m,u (1). From quantitative studies of simple proteins, this band could be correlated with the presence of tyrosine, tryptophan, and phenylalanine (2). A number of proteins exhibited absorption bands at wave-lengths above 280 rnp that could be interpreted in terms of a non-proteinaceous chromophore. Similarly, nucleoproteins show a maximum in the region of 260 rnp, which is associated with the presence of purine and pyrimidine nuclei (3). Most of the curves reported for proteins end at about 235 rnp on the short wave-length side of the main 280 mp peak, and, in this region, the absorption curves rise rapidly. Such a steep rise has led several investigators to assume that at shorter wave-lengths there is a region of continuous or end-absorption (4, 5). The specific structure of a protein that distinguishes it from other compounds is the presence of a large number of peptide bonds. Ley and Arends (6) and Rusoff et al. (7) studied the ultraviolet, absorption spectra of fatty acids, esters, anhydrides, and acid chlorides, and demonstrated that broad bands do exist in the region of 200 m/l. It seemed, therefore, that studies in the region below 240 rnp would be of interest.

Leo J. Saidel

Papers

The ultraviolet absorption spectra of proteins

The absorption spectra of amino acids in the region two hundred to two hundred and thirty millimicrons.

Threads in the hagfish slime gland thread cells: organization, biochemical features, and length.

Ultraviolet absorption spectra of proteins.

False Absorption Bands in the Region of 200-230 mµ Caused by Stray Radiation in the Beckman Spectrophotometer