Monomer Peak Research Articles

Concentration- and solvent-dependent electron spin resonance signals and dimer formation of high-spin iron(III) porphyrins

High-spin iron(III) prophyrins in frozen solutions show extra e.s.r. signals, in addition to the well known parallel (g= 2) and perpendicular (g= 6) absorption, which are remarkably sensitive to the concentration, solvent composition, pH, or the temperature. For example, two signals with g values around 3 and 11, respectively, are observed in moderately concentrated solutions of chloro(meso-nitro-octaethylporphyrinato)iron(III), in neutral and alkaline solutions of hemin when methanol is added, or in acidic solutions of tetrasodium phenylporphyrin-tetrasulphonatoferrate(III). The signals to higher field with g ca. 3 are interpreted as belonging to a dimeric species, on the basis of a simulation made by assuming a structure having two porphyrin planes arranged parallel. Another characteristic signal, which was observed in alkaline solutions of hemin or the tetrasodium ferrate, appears as a pair of shoulders with the g= 6 monomer peak in the middle. This type of signal is assigned to a dimer having a large Fe–Fe distance as well as skew angle. The effect of adding methanol, ethanol, or sucrose to the alkaline solutions of hemin, inducing further additional signals, and that of NaCl addition, which suppresses the overall intensity, are described and discussed in relation to previous studies by spectrophotometric and magnetic susceptibility measurements.

Photodisaggregation of chlorophyll a and b dimers

At room temperature, chlorophyll a (10/sup -4/M) in dry methylcyclohexane containing 0.01M methanol shows only the monomer peak at 661 nm. At -78/sup 0/C, it is partially converted to dimer, absorbing at 695 nm. Flash photolysis using a 30-ns ruby laser probe selectively excites and bleaches the dimer. The initial difference spectrum shows smaller bleaching in the Soret region and positive transients at 670 nm and in the triplet region 470 to 600 nm. These changes are completely reversible and correspond to cleavage of a dimer to produce triplet and ground-state units. The nascent monomer band at 670 nm is distinctly different from the original monomer (662), indicating a different mode of solvent coordination. The disaggregation demonstrated accompanies a decrease in acidity of magnesium/sup 2 +/ in the excited state. Chlorophyll b illustrates similar behavior. Photodisaggregation of the reaction centers has not been fully explained. 3 figures.

Altered nucleosome structure containing DNA sequences complementary to 19S and 26S ribosomal RNA in Physarum polycephalum.

The localization of DNA sequences coding for ribosomal RNA was studied by hybridization of purified ribosomal RNA to DNA from chromatin fragments prepared by limited digestion of Physarum nuclei with staphylococcal nuclease. The 32P-labeled 19S and 26S RNA hybridized to DNA from nucleosome monomers, dimers, trimers, and higher oligomers, separated by sucrose gradient centrifugation, although the level of hybridization to DNA from nucleosome fractions was less than the level of hybridization to undigested nuclear DNA. The distribution of 19S and 26S rDNA sequences in the nucleosome fractions differed from the distribution of bulk DNA in that the rDNA sequences were recovered primarily in two fractions containing monomer-sized DNA lengths (140-160 base pairs). The percentage of DNA hybridizing to 19S plus 26S RNA was greater in peak A, the more slowly sedimenting monomer peak, than in any other chromatin fraction at all stages of digestion. Peak A and monomer particles differed in protein content and distribution. The presence of ribosomal cistrons in an altered nucleosome configuration may be related to changes in functional states of rDNA chromatin.

Hemocyanins in spiders, IV[1]. Subunit heterogeneity of Eurypelma (Dugesiella) hemocyanin, and separation of polypeptide chains.

The hemocyanin of the North American tarantula Eurypelma californicum (Dugesiella californica) is dissociated at pH 9.6 into monomers (Mr about 70 000) and dimers (Mr about 140 000), which were separated by gel filtration. The monomer peak was resolved by preparative polyacrylamide gel electrophoresis and yielded 4 protein bands, three of which (1, 3 and 4M) are apparently homogeneous. Band 2 contains two sub-fractions (2I and 2II). The dimer peak contains two dimers (bands 4D and 5). Upon treatment with 5mM cysteine the dimer band 5 is dissociated, yielding only one type of monomer identical with band 3. The other dimer, which was only partially dissociated by 10mM EDTA, is most probably a heterodimer, one component being electrophoretically indistinguishable from band 2II. After treatment of the native hemocyanin with sodium dodecylsulfate and analysis in gradient gel slabs, 6 polypeptide chains were observed (labeled a - f). They correspond to the products of alkaline dissociation as follows: band 1 = e, band 2I = a, band 2II = c, band 3 = f, band 4M = d, band 4D = b plus c, band 5 = f. The molecular weights were determined by dodecylsulfate gel electrophoresis in gradient gels, and by sedimentation equilibrium analysis and found to range between 67 000 and 76 000. The sedimentation coefficients are between 4.4 and 4.7 S for the monomers and 6.6 and 6.7 for the dimers. The isoelectric points range from pH 4.5 to pH 5.4. The findings are discussed with respect to the limitations of molecular weight determination by conventional dodecylsulfate gel electrophoresis, to the structure of the hemocyanin oligomers and to possible biological significance.

The natural occurrence of insulin receptors in groups on adipocyte plasma membranes as demonstrated with monomeric ferritin-insulin.

AbstractThis study was designed to document whether the reported distribution of insulin receptors in small groups of receptor sites randomly distributed in the glycocalyx of adipocytes and isolated adipocyte plasma membranes was a naturally occurring phenomena or due to artifacts. Possible artifacts include: (1) oligomeric forms of ferritin in the ferritin‐insulin preparation, (2) an uneven distribution of the glycocalyx on the plasma membrane, or (3) ligand‐induced aggregation of occupied receptor complexes. Biogel A 1.5m chromatography of the ferritin‐insulin conjugate revealed the ferritin in the ferritin‐insulin complex to consist of 55% monomers, 15% dimers, and 30% oligomers. The monomer peak was purified (> 95%) for use in these studies. Cationic ferritin, a glycocalyx marker, when incubated with paraformaldehyde‐fixed plasma membranes, was found to be uniformly distributed on the surface of the plasma membrane indicative of uniformly distributed glycocalyx. The ability to demonstrate and inhibit ligand‐induced aggregation on the isolated plasma membrane was established with a multivalent ligand, ferritin‐concanavalin A. More than 66% of the ferritin‐concanavalin A receptors were found in large clusters of 5 or more and 34% as singletons or clusters of up to 4 when incubated at 24°C with fresh membranes. Only 38% of the ferritin‐concanavalin A receptors were in large clusters; 62% were singletons or clusters up to 4 on membranes prefixed with paraformaldehyde before incubation. The distribution of the monomeric ferritin‐insulin was similar on both adipocytes and purified adipocyte plasma membranes and was consistent with earlier reports with ferritin‐insulin. The quantitative distribution of the monomeric ferritin‐insulin as singletons or in groups of 2–6 was comparable between the intact cells and isolated membranes incubated at 24°C. The binding of 500 μUnits monomeric ferritin‐insulin per ml to the isolated plasma membranes was studied under incubation conditions similar to those used with ferritin‐concanavalin A. Under all three conditions, fresh membranes at 24°C and 0–4°C and prefixed membranes at 24°C, the pattern of distribution of the monomeric ferritin‐insulin as singletons or groups of 2–6 was identical, indicating that the ligand was not causing aggregation into clusters as did the concanavalin A. Thus, the occurrence of insulin receptors in small groups appears to be a natural phenomenon in the plasma membrane structure of adipocytes.

海産魚類新鮮肉および冷凍肉ミオシンのＤＥＡＥ‐ＳｅｐａｄｅｘＡ‐５０によるクロマトグラフィーと超遠心分析

In the previous work, we prepared myosins from the frozen muscle of a few marine fish species and compared the biochemical properties of these preparations. In this study, we investigated the chromatographic profiles and the ultracentrifugal diagrams of myosin preparations from frozen muscle of the same fish species. 1. The elution profiles obtained on DEAE Sephadex A-50 with myosins from skipjack tuna and white marline were similar to that obtained with myosin monomer from rabbit, while the profile obtained with myosin from yellowtail showed an crowded elution pattern suggesting a peak of myosin monomer overlapping with a small amount of myosin dimmer. 2. On ultracentrifugation, the sedimentation diagrams of myosins from skipjack tuna and white marline showed a hypersharp peak, characteristic of the myosin monomer from rabbit. The diagram of myosin from yellowtail, on the other hand, showed two peaks: a fast moving boundary presumably of myosin dimer, and a major slow moving one of myosin monomer. A study was also made on the properties of myosins from the fresh muscles of skipjack tuna and yellowtail. It was found that both myosins retained the properties characteristic of myosin monomer. It was, therefore, confirmed that yellowtail myosin is inevitably denatured during freezing and storage of fish muscle at -20°C.

メバチマグロおよびキハダマグロ冷凍肉ミオシンの比較

1) The Ca2+-ATPase activity (μmoles Pi per min per mg of protein) of bigeye tuna myosin was 0.10-0.25, and that of yellowfin tuna myosin was 0.70-0.85. The activity determination was carried out at 25°C in a reaction medium containing 50 mM KCl, 5mM CaCl2, 25mM Tris buffer (pH 7.0), and 1 mM ATP. 2) The ATP-sensitivity of synthetic actomyosin was also measured; it was 45-80 for bigeye tuna actomyosin, and 80-102 for yellowfin tuna actomyosin. 3) On ultracentrifugation, the sedimentation pattern of yellowfin tuna myosin showed a hypersharp peak characteristic of the myosin monomer (S20w=5.3S at protein concentration of 2.7 mg/ml). The pattern of bigeye tuna myosin, on the other hand, showed at least two peaks: a fast moving boundary presumably of myosin dimer, and a slow moving one of myosin monomer. 4) The elution profile on DEAE-sephadex A-50 chromatography was investigated. The profile obtained with yellowfin tuna myosin preparations was similar to that obtained with myosin monomer. On the other hand, the elution pattern of bigeye tuna myosin preparations showed a peak at void volume, probably of highly aggregated myosin, a peak of myosin dimer, and a peak of myosin monomer; the latter two peaks overlapping. It appears, therefore, that bigeye tuna myosin is somewhat denatured during the freezing and storage (-20°C) process.

Factor Analysis as a Complement to Band Resolution Techniques. III. Self Association in Trichloroacetic Acid

Digitized infrared spectra of nine solutions of trichloroacetic acid in CCl4 have been studied in the carbonyl stretching region. At all concentrations only two bands are visually apparent. However, factor analysis indicates the presence of four absorbing components. The contour resolution technique gives a monomer band at 1786 cm−1, a dimer band at 1749 cm−1, and a third band close to the dimer frequency at approximately 1735 cm−1. Examination of the changes in Cauchy–Gauss shape ratio of the monomer band with increasing concentration indicates the presence of an unresolved component. The band at 1735 cm−1 and the unresolved band near the monomer peak at 1786 cm−1 are assigned to absorption of carbonyl groups in linear polymers of trichloroaceticacid. The monomer–dimer equilibrium constant was calculated from the molar absorption coefficients and absorbances of monomer and dimer bands. The average value over the concentration range 0.305 × 10−3 to 0.1603 M was 287 l/mol at 33.9 ± 0.5 °C.

Treatment of Bovine Nasal Cartilage Proteoglycan with Chondroitinases from Flavobacterium heparinum and Proteus vulgaris

Abstract A colorimetric procedure was developed for assaying the enzyme activity of chondroitinase AC from Flavobacterium heparinum and of chondroitinase ABC from Proteus vulgaris when chondroitin 4-sulfate is used as a substrate. The enzymatic digestion product, 2-acetamido-2-deoxy-3-O-(β-d-gluco-4-enepyranosyluronic acid)-4-O-sulfo-d-galactose, is oxidized with periodic acid to yield, among other products, formylpyruvic acid. The latter compound reacts with thiobarbituric acid to yield a chromophore with an absorption maximum at 549 nm. Both enzymes were used to remove chondroitin sulfate from bovine nasal cartilage proteoglycan. The protein-keratan sulfate core isolated after limit digestion of proteoglycan with chondroitinase AC contains about 44% protein, 38% keratan sulfate, and 18% of the enzymatically modified oligosaccharide attachment region between the chondroitin sulfate chains and protein core: gluco-4-enepyranosyluronic acid-(galactosyl)2-xylose. Limit digestion of proteoglycan with chondroitinase ABC leaves a residual disaccharide on the chondroitin sulfate chains in the core preparation. Both monomeric and aggregated preparations of proteoglycan were treated with chondroitinase AC and the resulting core fractions were studied in the ultracentrifuge. A single, fairly symmetrical peak with a sedimentation coefficient of 7.7 S was observed for the core prepared from monomeric proteoglycan. In addition to this monomeric peak, the core prepared from aggregated proteoglycan exhibited a faster sedimenting, broad peak with a sedimentation coefficient of about 18 S. The results indicate that the noncovalent interactions which are essential for the aggregation of proteoglycans do not require the presence of the chondroitin sulfate portion of the macromolecules.

Dye aggregations or crystals within the void places of polyvinyl alcohol fibre

The visible absorption spectra of the cross-section of dyed PVA fibre with AO were measured by means of a microspectrophotometer. The spectra showed a high maximum at 475 nm, which would be referred to as β-band (a monomer peak at 498 nm). Many void places were recognized in core layer by electron or scanning electron microscopy. It was explained that the dimer band mainly arose from dye aggregates or crystals at the void places of fibre.

Dye aggregations or crystals within the void places of viscose film

The visible absorption spectra of the cross-sections of dyed viscose films were measured by means of a microspectrophotometer. We found that the spectra of Acridine Orange in the cross-sections of films showed a high maximum at 475 mμ, which would be referred to as β-band (a monomer peak at 497 mμ). It was explained from microscopic photographs and electron microscopic photographs that the dimer band arises from dye aggregates or crystals at the void places of viscose film.

Experimental protein-calorie malnutrition in rats: Biochemical and ultrastructural studies

Young rats (100–130 gm) fed a low-protein diet which simulates the protein value of diets eaten by children in areas where protein-calorie malnutrition is prevalent developed many of the features associated with kwashiorkor. Among the findings were marked loss in body weight, atrophy of many visceral organs, fatty liver, hypoproteinemia, edema, and profound changes in serum amino acid patterns. Associated with the alterations in serum amino acid levels were extreme disproportions in the fasting levels of amino acids in liver. This experimental model of rodent kwashiorkor showed marked reduction in liver protein and RNA contents, but DNA remained remarkably constant indicating loss of cellular contents rather than decrease in cell population. The decreased RNA content of the liver was consistent with the observations of massive breakdown of the membranes of the endoplasmic reticulum as well as the elevated activity of alkaline ribonuclease assayed in the absence of PCMB. The polysomes showed extensive disaggregation resulting in increased monomer and dimer peaks. The significance of these biochemical and anatomical changes as well as their possible relevance to kwashiorkor in children was discussed.

Proein-synthetic activity of ribosomes from interferon-treated cells.

Cell-free protein-synthetic systems from normal and interferon-treated chick cells were compared. No difference was found in the amino acid incorporation activities of such ribosome-cell sap systems or in their response to polyuridylic acid. Throughout a variety of experiments we failed to detect the formation of a discrete peak of virus-specific polysomes, when ribosome monomers and subunits (from interferon-treated or control cells) were incubated with labeled Sindbis or Semliki Forest virus ribonucleic acid (RNA). Some binding of viral RNA did occur, but the complexes formed were evident in sucrose gradients as a broad, rapidly sedimenting shoulder on the ribosome monomer peak. Interferon pretreatment of cells did not affect the formation of these complexes in vitro, nor did it alter their rate of breakdown on incubation under amino acid incorporation conditions. Experiments with inhibitors of protein synthesis showed that such "breakdown" was not dependent upon amino acid incorporation and was not an index of translation. In these respects, our results are in marked contrast to those of Marcus and Salb. These results, together with our failure to detect any significant change in the protein composition of ribosomes from interferon-treated cells, suggest that such treatment does not result in a modification of the ribosome per se. They do not, however, rule out the involvement of a factor(s) required for ribosomes and viral RNA to function in viral protein synthesis. Indeed, it remains likely that interferon acts through such a mechanism, although the precise level at which the inhibition occurs remains to be elucidated.

Self-association of alcohols and phenols in nonpolar solvents

A number of alcohols (primary, secondary, and tertiary) and phenols, covering a pKa range from 9.4 to 19.0, gave on association a peak about 125 ± 5 cm−1 lower than the monomeric hydroxyl peak in the fundamental stretching region. Taken together with the extensive literature available on the association of alcohols and phenols in nonpolar solvents, this seems to indicate the presence of dimers.

Reversible Dissociation of Tetrameric Rabbit Muscle Glyceraldehyde 3-Phosphate Dehydrogenase into Dimers or Monomers by Adenosine Triphosphate

Abstract Tetrameric 7.5 S rabbit muscle glyceraldehyde 3-phosphate dehydrogenase is dissociated by ATP at 0° into 4.5 S dimers or 2.8 S monomers, depending upon the protein concentration. Dissociation into two peaks is observed at protein concentrations as high as 10 mg per ml, and a 4.5 S dimer is produced in increasing quantity from the 7.5 S tetramer as the protein concentration is lowered from 10 to 2 mg per ml. At 1 mg per ml, a single 4.2 S dimer peak is observed, and at 0.1 mg per ml, a single 2.8 S monomer peak is observed. Between 1.0 and 0.1 mg per ml, only single peaks with sedimentation coefficients intermediate to those of the dimer and monomer are observed, suggesting a fairly rapidly equilibrating mixture of 2.8 S monomers and 4.5 S dimers in varying amounts. The observed inactivation is only slight at temperatures down to 12°, but the equilibrium is shifted fairly strongly toward inactive subpolymers at 7° and apparently is shifted completely to inactive monomers at 0° at 0.05 mg per ml of enzyme. The dissociation has practically no pH dependence in the range of 6.5 to 9.5, but it is somewhat greater and faster at pH 5.5 than at all others studied. Inactivation and dissociation are reversed by rewarming the enzyme to 23° and removing the ATP. Ammonium sulfate, 1 m, or 2 mm NAD protects against inactivation and dissociation. Dissociation is faster with ATP than with other adenine nucleotides and much faster and more pronounced with ATP than with GTP, UTP, CTP, FAD, and CoA.

Polyribosomes of Escherichia coli: II. Experiments to determine the in vivo distribution of polysomes, ribosomes and ribosomal subunits

A study was made to determine the most probable in vivo distribution of polysomes, ribosomes and ribosomal subunits in early log-phase Escherichia coli. Experimental conditions for obtaining a type I-polysome profile in which there is little or no 70 s monomers were compared to those for obtaining a type II profile in which 12 to 15% of the ribosomes are present as 70 s monomers. Polysome profiles of lysates of E. coli strains with decreasing endogenous ribonuclease activity (strains 3000, Q13, 1113B) were almost identical, which suggested that the 70 s monomers of a type II profile were not derived from polysomes by endogenous ribonuclease activity. Furthermore, purified ribonuclease II degraded neither the larger polysomes in a lysate nor isolated polysome dimers. Even in 60 m m-KCl, where one finds a large peak of ribosomes, addition of yeast RNA oligonucleotides to the lysate and to the sucrose gradients results in suppression of the monomer peak. The same effect can be obtained with higher concentrations of KCl in the lysate and the sucrose gradient. On the other hand, isolated 70 s monomers are stable when centrifuged through gradients containing RNA oligonucleotides or high KCl concentrations. These are all conditions which will inhibit the activity of E. coli RNase II but are also conditions which block initiation of protein synthesis. Polysome profiles were also examined in E. coli lysates to which various inhibitors of protein synthesis were added: chloramphenicol, dihydro-streptomycin, mikamycin, sparsomycin and tetracycline. The results indicated that the 70 s monomers observed in type II profiles were formed in vitro after cell lysis by association of native 50 s and 30 s ribosomal subunits to form 70 s complexes. Studies with trimethoprim and puromycin, which were used as in vivo inhibitors of protein synthesis, supported this hypothesis. Further support of this hypothesis came from analyzing the pulse-labeled RNA associated with the 70 s monomer in TMK § § Abbreviations used: TM buffer is 0.005 m-Tris pH 7.4 at 5 °C, with 0.01 m-MgSO 4; TMK is TM buffer containing 60 m m-KCl; TMNa is TM buffer containing 60 m m-NaCl; TCGl is Tris-Casamino acid-glycerol synthetic medium (cf. Franklin, 1966); STE is 0.1 m-NaCl, 0.05 m-Tris buffer, pH 7.2 at 0 °C, 0.001 m-EDTA; TS is Tris (0.1 m)-sucrose (20% w v ), pH 8.1 at 5 °C; PNPase is polynuoleotide phosphorylase. lysates. This RNA, which is mostly messenger RNA, should be degraded if the 70 s peak arises from breakdown of polysomes and should be heterogeneous and large if the 70 s peak represents artifactual 70 s monosemes formed with intact mRNA. The latter was found to be true. Also, it was possible to obtain a small amount of association of isolated 50 and 30 s subunits to form a 70 s complex when they were mixed with spheroplasts prior to lysis in TMK but not in TMNa. In conclusion, all of our experiments suggest that the type I profile is probably most representative of the in vivo distribution of polysomes, ribosomes and ribosomal subunits in early log-phase E. coli.

Analysis of polystyrene and related resins by pyrolysis gas chromatography

Pyrolysis gas chromatography was used for the determination of the monomeric composition of some hydrocarbon resins resulting from the liquid product of naphtha pyrolysis. The effect of working conditions on the peak composition of the pyrogram was investigated. From the monomer peak areas corrected by experimental factors the monomeric composition of a copolymer can be calculated.

Distribution of newly synthesized amylase in microsomal subfractions of guinea pigs pancreas.

Amylase distribution was studied in guinea pig pancreas microsomes fractionated by centrifuging, for 2 hr at 57,000 g in a linear 10 to 30% sucrose gradient, a resuspended high speed pellet obtained after treating microsomes with 0.04% deoxycholate (DOC).(1) Amylase appeared in the following positions in the gradient: (a) a light region which contained approximately 35% of total enzymic activity and which coincided with a monomeric ribosome peak; (b) a heavy region which contained approximately 10% of enzymic activity in a sharp peak but which had very little accompanying OD(260) absorption; (c) a pellet at the bottom of the centrifuge tube which contained approximately 20% of the enzymic activity. After 5 to 20 min' in vivo labeling with leucine-1-C(14), radioactive amylase was solubilized from these three fractions by a combined DOC-spermine treatment and purified by precipitation with glycogen, according to Loyter and Schramm. In all cases, the amylase found in the pellet had five to ten times the specific activity (CPM/enzymic activity) of the amylase found in the light or heavy regions of the gradient. The specific radioactivity (CPM/mg protein) of the proteins or peptides not extracted by DOC-spermine was similar for all three fractions. Hypotonic treatment of the fractions solubilized approximately 80% of the total amylase in the fraction from the heavy region of the gradient, but only approximately 20% of the amylase in the monomer or pellet fraction. Electron microscope observation indicates that the monomer region of the gradient contained only ribosomes, that the heavy region of the gradient contained small vesicles with relatively few attached ribosomes, and that the pellet was composed mostly of intact or ruptured microsomes with ribosomes still attached to their membranes. It is concluded from the above, and from other evidence, that most of the amylase activity in the monomer region is due to old, adsorbed enzyme; in the heavy region mostly to enzyme already inside microsomal vesicles; and in the pellet to a mixture of newly synthesized and old amylase still attached to ribosomes. Furthermore, the ribosomes with nascent, finished protein still bound to them are more firmly attached to the membranes than are ribosomes devoid of nascent protein.

Distribution studies of tripropyl phosphate between different organic diluents and water

The distribution of radioactive (PrO) 3PO between water and the following mixtures of organic diluents was measured at 25°C: carbon tetrachloride, methylisobutyl ketone (hexone), tributyl phosphate (TBP), tripropyl phosphate (TPP) and chloroform with hexane, and hexone, tributyl phosphate and chloroform with carbon tetrachloride. These experiments have shown the following order of interaction between TPP and the solvents: chloroform (5·4) > TBP (2·4) > hexone (1·0) > carbon tetrachloride (0·8) > hexane. The numbers refer to the constants K of the following equilibrium in water-saturated hexane: TPP + S ⤦ TPP·S Additional distribution experiments were made with hexane or carbon tetrachloride and nitric acid or sodium hydroxide solutions. Since our distribution measurements indicated that the interaction between trialkyl phosphates and the diluents depends mainly on the PO group, we suggest that the distribution data for TPP can be used to estimate the activity of TBP in solvent mixtures. Our results are in good agreement with vapour pressure measurements by Rozen et al. (1) of TBP mixtures with hexane and carbon tetrachloride. Infra-red measurements on TBP in different diluents show a definite influence of carbon tetrachloride, TBP, hexone, and chloroform on the PO stretching vibration of TBP. Using TBP-hexane mixtures and K = 2·4 we were able to resolve the absorbance peaks of the PO group into a split peak of the TBP monomer and an unsplit peak of (TBP) 2.

Effect of Pressure on the Optical Properties of Organic Phosphors

The effect of pressure to 54 kbar has been measured on absorption spectra, emission spectra, and decay rates of four organic phosphors. For fluorescein and dichlorofluorescein the decay rate increases with increasing pressure. The emission spectrum consists of two peaks which approach each other at high pressure. Thus there appears to be an increased mixing of triplet and excited singlet states at high pressure. For acridine yellow and orange the absorption spectrum shows a dimer and monomer peak. The dimer peak decreases rapidly in intensity with increasing pressure. At high concentrations the component decay rates are largely independent of pressure. At lower concentrations the decay rate becomes slower at higher pressure. Evidently the emission can be associated with the dimer.