Difference In Absorption Maxima Research Articles

Highly sensitive detection of bovine serum albumin based on the aggregation of triangular silver nanoplates

A simple, fast and highly sensitive spectrophotometric method for the determination of bovine serum albumin (BSA) has been developed based on the interactions between triangular silver nanoplates (TAgNPs) and BSA in the presence of Britton–Robison buffer solution (BR). Particularly, the wavelength of absorption maximum (λmax) of TAgNPs is red shifted in the presence of BSA together with Britton-Robinson buffer solution (BR, pH=2.56), and the color of the solution changed from blue to light blue. This may be due to the interactions between BSA molecules on the surface of TAgNPs through electrostatic forces, hydrogen bonds, hydrophobic effects and van der Waals forces at pH2.56, which leads to the aggregation of TAgNPs. The determination of BSA was achieved by measuring the change of λmax corresponding to localized surface plasmon resonance (LSPR) from UV–visible spectrophotometry. It was found that the shift value in the wavelength of absorption maximum (Δλ, the difference in absorption maxima of the TAgNPs/BSA/BR mixture and the TAgNPs/BR mixture) was proportionate to the concentration of BSA in the range of 1.0ngmL−1 to 100.0ngmL−1 with the correlation coefficient of r=0.9969. The detection limit (3σ/k) for BSA was found to be as low as 0.5ngmL−1.

Solution and Solid-State Spectra of Quinacridone Derivatives as Viewed from the Intermolecular Hydrogen Bond

Quinacridones are industrially important hydrogen-bonded pigments. The color in the solid state is vivid red, while it is pale yellow in solution, indicating evidently the involvement of intermolecular interactions in the solid state. The electronic structure has therefore been investigated with special attention to the role of intermolecular NH...O hydrogen bonds for three representative quinacridone compounds with different hydrogen-bond forming characteristics: unsubstituted gamma-quinacridone (gamma-QA) with two NH groups, mono-N-methylquinacridone (MMQA) with one NH and one CH(3), and N,N'-dimethyl-quinacridone (DMQA) with two CH(3) groups. The number of the NH...O hydrogen bonds per molecule is four, two, and zero for gamma-QA, MMQA, and DMQA, respectively. In solution, no significant difference in absorption maximum is recognized between gamma-QA, MMQA, and DMQA. However, in the solid state, the absorption maximum of gamma-QA appears at the longest wavelength, followed by MMQA and then DMQA, depending on the number of NH...O intermolecular hydrogen bonds. The role of the hydrogen bond is found to align transition dipoles in a "head-to-tail" fashion and to displace the absorption band toward longer wavelengths due to excitonic interactions. The extent of the spectral shift increases with increasing number of hydrogen bonds per molecule.

Synthesis, spectroscopic properties and thermal stability of metal(II) tetraazaporphyrin complexes with two strong wavelength absorption

Three kinds of metal(II) tetraazaporphyrin complexes with blue-violet and red light wavelength absorption were synthesized by refluxing tetraazaporphyrin ligand and different metal(II) ions, respectively. Their structures were confirmed by elemental analysis, LDI-TOF-MS, FT-IR and UV–Vis. The solubility of metal(II) tetraazaporphyrin complexes in organic solvents and absorption properties of their chloroform solution and films on K9 glass in the region 250–800 nm were measured. The influence on the difference of absorption maximum from metal(II) tetraazaporphyrin complexes to tetraazaporphyrin ligand by different metal(II) ions was studied. In addition, the thermal stability of the complexes was also evaluated.

Synthesis and spectroscopic properties of new azo-dyes and azo-metal complexes derived from barbituric acid and aminoquinoline

Two new azo-dyes, 5-(quinoly-8-azo)pyrimidine-2,4,6-trione ( L 1 ) and 5-(quinoly-8-azo)-1,3-dimethylpyrimidine-2,4,6-trione ( L 2 ) were prepared by linking 8-aminoquinoline to barbituric acid and 1,3-dimethylbarbituric acid through diazo-coupling reactions. Reaction of new azo-dyes with Cu(II) or Ni(II) salts and unidentated ion gave mononuclear complexes with general stoichiometry [MLX], [M: Ni(II) or Cu(II); X: NO 3 −, SCN −, CN − or N 3 −]. On the other hand, two kinds of cobalt(II) complexes with different stoichiometries were prepared. Reaction of azo-dyes with Co(AcO) 2 with 2:1 molar ratio gave azo complexes with stoichiometry Co(L) 2 while reaction of cobalt salts with tridentate azo-dyes, bidentate ligand, 1,10-phenanthroline ( B), and unidentate ion (X: NO 3 −, SCN −, CN − or N 3 −), mixed hard–soft donor sets, produced a new set of complexes with general stoichiometry CoLBX. The structures of both azo-dyes and their complexes were identified by elemental analyses, FTIR, 1H NMR, UV–vis, magnetic susceptibility and mass spectral data. The elemental analyses and spectral data indicate that azo-dyes act as monobasic O, N, N′-tridentate ligand. The difference in absorption maximum from ligands to metal complexes was also studied.

A Colorimetric and Fluorometric Chemosensor Based on Quinizarin-Metal Complexes for Alkaline Phosphatase Activity

Hydroxyanthraquinones are well known colorimetric indicators for pH and metal ions. In high pH media, these substances exist in phenolate anionic forms, which have absorption maxima in the visible region. In addition, hydroxyanthraquinone phenolates readily bind metal ions, such as magnesium and aluminum, to produce highly fluorescent metal-anthraquinone complexes. For example, a greater than 30 fold increase of fluorescence intensity is observed when 1,4-dihydroxyanthraquinone (quinizarin, QNZ, 1) complexes with aluminum ion. Tight binding by these quinizarins is due to metal ion interactions with the ionized hydroxyl groups and neighboring carbonyl moieties, as depicted in 2. If the hydroxyl groups of these substances are protected, metal-QNZ complex formation does not take place. Moreover, significant differences in absorption maxima and fluorescence intensities are expected for protected and metal complexed QNZ. Thus, appropriately protected QNZs should serve as dual signal (colorimetric and fluorometric) chemosensors for processes (e.g., enzymatic) that promote cleavage of the hydroxyl protecting groups. In this communication, we report, the results of initial studies leading to the development of a hydroxyquinone-based, enzyme-cleavable colorimetric and fluorometric chemosensor, quinizarin diphosphate (QDP, 3), and its application to a method for assaying alkaline phosphatase activity.

Polymorph of N, N′-di- n-butylperylene-3,4:9,10-bis(dicarboximide) and their electronic structure

Perylene pigments are known to exhibit a variety of shades in the solid state from vivid red, via maroon to black, although their solution spectra are quite similar. A second phase of the title compound (phase II) has newly been found when the single crystals were grown from the vapor phase. Phase II bears a black color while the previous phase (phase I) exhibits red-maroon. For this reason, the electronic structure of both phases has been investigated on the basis of the crystal structure as well as intermolecular interactions. In both phases, the absorption spectrum is composed of two bands: one is due to individual molecules (i.e. around 450–550 nm) and the second band arises from excitonic interactions between transition dipoles (i.e. around 600 nm in phase I and 625 nm in phase II). The intermolecular interactions along the stacking axis are primarily responsible for the appearance of the second band in both phases. Additionally, the interaction on the molecular plane is found to be slightly hypsochromic in phase I while bathochromic in phase II. This induces a difference in absorption maximum of the second band, leading to two different colors (red-maroon and black) in phases I and II.

Rare earth doped β-diketone complexes as promising high-density optical recording materials for blue optoelectronics

Some kinds of rare earth β-diketone complexes with blue-violet light absorption edge were synthesized using the ligands of thenoyltrifluoroacctone (HTTA), 2, 2′-dipyridyl (BIPY) and different metal ions (Gd3+, Sm3+ and La3+). Their contents, structures and optoelectronic parameters were monitored by elemental analysis, MS, IR and UV spectra. The solubility of rare earth β-diketone complexes in 2, 2, 3, 3-tetrafluoro-1-propanol (TFP) and absorption properties of their films in the region 300–800 nm were measured. The influence on the difference of absorption maximum from rare earth β-diketone complexes to β-diketone ligand by different metal ions was studied. In addition, the thermal stability of rare earth β-diketone complexes was also reported.

Synthesis, spectroscopic and thermal properties of nickel (II)–azo complexes with blue-violet light wavelength

A novel azo dye containing isoxazole ring and β-diketone derivative (TIAD) and its two nickel (II) complexes (Ni (II)–ETIAD and Ni (II)–HTIAD) were synthesized in order to obtain a blue-violet light absorption and better thermal stability as a promising organic storage material for next generation of high density digital versatile disc-recordable (HD-DVD-R) systems that uses a high numerical aperture of 0.85 at 405 nm wavelength. Their structures were confirmed on the basis of elemental analysis, MS, FT-IR, UV–Vis and magnetic data. Their solubility in 2,2,3,3-tetrafluoro-1-propanol (TFP) and absorption properties of thin film were measured. The difference of absorption maximum from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated.

Molecular genetics of color-vision deficiencies

The normal X-chromosome-linked color-vision gene array is composed of a single long-wave-sensitive (L-) pigment gene followed by one or more middle-wave-sensitive (M-) pigment genes. The expression of these genes to form L- or M-cones is controlled by the proximal promoter and by the locus control region. The high degree of homology between the L- and M-pigment genes predisposed them to unequal recombination, leading to gene deletion or the formation of L/M hybrid genes that explain the majority of the common red-green color-vision deficiencies. Hybrid genes encode a variety of L-like or M-like pigments. Analysis of the gene order in arrays of normal and deutan subjects indicates that only the two most proximal genes of the array contribute to the color-vision phenotype. This is supported by the observation that only the first two genes of the array are expressed in the human retina. The severity of the color-vision defect is roughly related to the difference in absorption maxima (lambda(max)) between the photopigments encoded by the first two genes of the array. A single amino acid polymorphism (Ser180Ala) in the L pigment accounts for the subtle difference in normal color vision and influences the severity of red-green color-vision deficiency. Blue-cone monochromacy is a rare disorder that involves absence of L- and M-cone function. It is caused either by deletion of a critical region that regulates expression of the L/M gene array, or by mutations that inactivate the L- and M-pigment genes. Total color blindness is another rare disease that involves complete absence of all cone function. A number of mutants in the genes encoding the cone-specific alpha- and beta-subunits of the cGMP-gated cation channel as well as in the alpha-subunit of transducin have been implicated in this disorder.

Synthesis of blue-violet light wavelength metal (II)-azo complexes and their absorption and thermal properties

Some kinds of metal (II)-azo complexes with blue-violet light wavelength absorption were synthesized using a diazo component, a coupling component and different metal ions (Cu 2+, Ni 2+and Zn 2+). Their structures were confirmed by elemental analysis, spectral and magnetic data. The solubility of metal (II)-azo complexes in 2, 2, 3, 3-tetrafluoro-1-propanol (TFP) and absorption properties of their films in the region 300–800 nm were measured. The influence on the difference of absorption maximum from metal (II)-azo complexes to azo ligand by different metal ions was studied. In addition, the thermal stability of metal (II)-azo complexes was also reported.

Synthesis and absorption properties of some new azo-metal chelates and their ligands

Some new azo-metal chelates were synthesized using different diazo components, coupling components and metal ions. Their structures were confirmed by IR spectra, MS spectra and UV–Vis spectra. Their solubility in 4-hydroxy-4-methyl-2-pentanone and absorption properties of film were measured. The influence on the difference of absorption maximum from azo-metal chelates to their ligands by diazo components, coupling components and metal ions was studied.

Genetics of color vision deficiencies.

The normal X-chromosome-linked color vision gene array is composed of a single red pigment gene followed by one or more green pigment genes. The high degree of homology between these genes predisposed them to unequal recombination, leading to gene deletions or the formation of red-green hybrid genes that explain the majority of the common red-green color vision deficiencies. Gene expression studies suggest that only the two most proximal genes of the array are expressed in the retina. The severity of the color vision defect is roughly related to the difference in absorption maxima of the photopigments encoded by the first two genes of the array. A single amino acid polymorphism (Ser180Ala) in the red pigment accounts for the subtle difference in normal color vision and influences the severity of color vision deficiency. Blue cone monochromacy is a rare disorder that involves absence of red and green cone function. It is caused either by deletion of a critical region that regulates expression of the red/green gene array, or by mutations that inactivate the red and green pigment genes. Total color blindness is another rare disease that involves complete absence of all cone function. A number of mutations in the genes encoding the cone-specific alpha- and beta-subunits of the cation channel and the alpha-subunit of transducin have been implicated in this disorder.

Synthesis and a UV and IR spectral study of some 2‐aryl‐Δ‐2‐1,3,4‐oxadiazoline‐5‐thiones

AbstractTwenty four 2‐Aryl‐Δ‐2‐1,3,4‐oxadiazoline‐5‐thione derivatives 2 were synthesized and their uv and ir spectra were studied. Correlation between σ‐Hammett constants of aryl substituents and the differences in absorption maxima (Δv = v1‐v2 in kK) of the electronic spectra of the deprotonated species were also evaluated. A new method for the synthesis of the 2‐(amino)aryl derivatives 2v,w,x is also reported.

IODOPSIN, A RED‐SENSITIVE CONE VISUAL PIGMENT IN THE CHICKEN RETINA*

The vertebrate retina contains two kinds of visual cells: rods, responsible for twilight (scotopic) vision (black and white discrimination); and cones, responsible for daylight (photopic) vision (color discrimination). Here we attempt to explain some of their functional differences and similarities in terms of their visual pigments. In the chicken retina there are four types of single cones and a double cone; each of the single cones has its own characteristic oil droplet (red, orange, blue, or colorless) and the double cone is composed of a set of principal and accessory members, the former of which has a green-colored oil droplet. Iodopsin, the chicken red-sensitive cone visual pigment, is located at outer segments of both the red single cones and the double cones, while the other single cones and the rod contain their own visual pigments with different absorption spectra. The diversity in absorption spectra among these visual pigments is caused by the difference in interaction between chromophore (11-cis retinal) and protein moiety (opsin). However, the chromophore-binding pocket in iodopsin is similar to that in rhodopsin. The difference in absorption maxima between both pigments could be explained by the difference in distances between the protonated Schiff-bases at the chromophore-binding site and their counter ions in iodopsin and rhodopsin. Furthermore, iodopsin has a unique chloride-binding site whose chloride ion serves for the red-shift of the absorption maximum of iodopsin. Visual pigment bleaches upon absorption of light through several intermediates and finally dissociates into all-trans retinal and opsin. That the sensitivity of cones is lower than rods cannot be explained by the relative photosensitivity of iodopsin to rhodopsin, but may be understood to some extent by the short lifetime of an enzymatically active intermediate (corresponding to metarhodopsin II) produced in the photobleaching process of iodopsin. The rapid formation and decay of the meta II-intermediate of iodopsin compared with metarhodopsin II are not contradictory to the rapid generation and recovery of cone receptor potential compared with rod receptor potential. The rapid recovery of the cone receptor potential may be due to a more effective shutoff mechanism of the visual excitation, including the phosphorylation of iodopsin. The rapid dark adaptation of cones compared with rods has been explained by the rapid regeneration of iodopsin from 11-cis retinal and opsin. One of the reasons for the rapid regeneration and susceptibility to chemicals of iodopsin compared with rhodopsin may be a unique structure near the chromophore-binding site of iodopsin.

Differently oriented chlorophylls in Mesotaenium caldariorum detected by microphotometrical dichroism measurements in vivo

The chloroplasts of individual cells of Mesotaenium caldariorum were examined microphotometrically under non-polarized and polarized measuring light. The measurement with non-polarized light showed different absorption bands of the thylakoids depending on the position of their surface with respect to the incident light beam: in the edge position, the absorption bands lie at 672 nm, in the face position at 678 nm. From this difference in absorption maxima, we conclude that the molecules related to the sub-bands at the two wavelengths are oriented differently. The Q y transition of the molecules which absorb light at 678 nm must be oriented parallel to the face of the thylakoids (fraction I), while that of the molecules absorbing at 672 nm is oriented perpendicular to the face (fraction II). Measurement with polarized light leads to the same conclusion that two fractions of differently oriented chlorophylls exist: In the edge position, a very large difference between E ∥ and E ⊥ (dichroism) was found in red light, with a maximum of E ∥ lying at 675 nm and a maximum of E ⊥ at 670 nm, with a shoulder at 650 nm. In the blue region, especially in the Soret band zone, the chloroplast showed a negative dichroism in the edge position, which changes over to positive values when the wavelength exceeds 450 nm. In the face position no dichroism in red or blue light could be detected. Comparison of the ‘edge position dichroism’ in red light with that in blue light justifies the supposition that the chlorin planes of the chlorophyll molecules may be oriented perpendicular or parallel to the thylakoid face, in the case of perpendicular orientation with the Q y transitions of fraction II and the x-transitions ( B x , Q x ) of fraction I projecting out of the plane, and for parallel orientation with all transition moments lying parallel to the plane (fraction I). The relative dichroism, (E ∥ − E ⊥) (E ∥ + E ⊥) , measured at the edge position amounts to 0.34 (i.e., 34% of the total absorption) at 680 nm. These data probably do not reflect the total quantity of oriented chlorophyll because from the opposite orientations of the Q y transition moments of fraction I and II pigment a partial quenching of the measurable dichroism results. The red light absorption bands of the two chlorophylls oriented in an opposite manner (fractions I and II) correspond to the known bands of Photosystem I and II.

Effects of solvent on the absorption maxima of five-coordinate heme complexes and carbon monoxide-heme complexes as models for the differential spectral properties of hemoglobins and myoglobins.

Absorption spectra were recorded for 5- and 6-coordinate model ferrous heme complexes of hindered and unhindered ligands in aqueous, and detergent solutions. Heme complexes exhibited differences in absorption maxima up to 6 nm which were correlated with the polarity of the heme environment. Increasing polarity of the solvent resulted in a general blue shift of absorption maxima of both deoxy- and (carbon monoxy)heme complexes. The differences in absorption maxima of heme complexes with different heme environments are offered as a possible explanation for some of the differences in absorption maxima among hemoproteins such as hemoglobin, myoglobin, and leghemoglobin.

The spectrophotometric evaluation of mixtures of methylene blue and trimethyl thionin

Spectrophotometric analysis affords the most convenient means for determining the proportion of methylene blue and trimethyl thionin (azure B) present in a mixture of these two dyes. The method proposed depends upon the determination of an “absorption ratio.” A suitable ratio for the purpose is that of the extinction coefficient at 640 mμ to that at 670 mμ. On account of the difference in absorption maxima of the two dyes, this ratio increases as the percentage of methylene blue decreases. The ratio value for eleven different mixtures is given and a graph is plotted from this data by means of which the proportions of the two dyes present in any mixture can be calculated from the absorption ratio determined as specified.

The Spectrophotometric Evaluation of Mixtures of Methylene Blue and Trimethyl Thionin

Spectrophotometric analysis affords the most convenient means for determining the proportion of methylene blue and trimethyl thionin (azure B) present in a mixture of these two dyes. The method proposed depends upon the determination of an “absorption ratio.” A suitable ratio for the purpose is that of the extinction coefficient at 640 mμ to that at 670 mμ. On account of the difference in absorption maxima of the two dyes, this ratio increases as the percentage of methylene blue decreases. The ratio value for eleven different mixtures is given and a graph is plotted from this data by means of which the proportions of the two dyes present in any mixture can be calculated from the absorption ratio determined as specified.