Visual Pigments of Goldfish Cones : Spectral Properties and Dichroism

Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 ± 3,530 ± 3, and 625 ± 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2–3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400–410, 435–455, and 350–360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene₂ is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 ± 0.0015/µm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Δν = 4,832 ± 100 cm^–1. The red-absorbing spectrum was found narrower, having Δν = 3,625 ± 100 cm^–1. The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra.     

Isolation of oligomers of 5,6-dihydroxyindole-2-carboxylic acid from the eye of the catfish

The reflecting material of the tapetum lucidum of the sea catfish (Arius felis) was chromatographed on Sephadex LH-20 in methanol–dimethyl sulphoxide–formic acid. Two components were present: one, showing an absorption maximum at 330nm, was tapetal pigment; the other, at 257nm, was an associated nucleoside. The tapetal pigment was extracted in methanol–HCl and isolated by adsorption chromatography on Sephadex LH-20. It yielded a methoxy methyl ester on treatment with diazomethane, and permanganate oxidation gave pyrrole-2,3,5-tricarboxylic acid. From the information provided by u.v. and i.r. spectra of the pigment and its methoxy methyl ester, from elemental analyses and from the oxidation products, we suggest that the tapetal pigment is derived from oxidative coupling of 5,6-dihydroxyindole-2-carboxylic acid. A molecular-weight determination and chromatography of the methoxy methyl ester indicate that the pigment is a mixture of oligomers, among which the tetramers probably predominate. We consider that the monomers are joined mainly by C-C linkages at positions 4 and 7. A synthetic pigment having spectral properties nearly identical with those of the natural pigment was prepared by enzymic oxidation of 5,6-dihydroxyindole-2-carboxylic acid with mushroom tyrosinase. The identity of the tapetal pigment with the synthetic pigment was further confirmed by comparing u.v. and i.r. spectra of their methoxy methyl esters. Formation of the tapetal pigment from tyrosine and relationships of the tapetal pigment to melanin are discussed.     

Heterogeneity and tissue specificity of tropomyosin isoforms from four species of bivalves

Heterogeneity and tissue specificity of tropomyosin isoforms obtained from four species of bivalves (Scapharca broughtonii (ark shell), Mytilus galloprovincialis (mussel), Atrina pectinata (surf clam) and Crassostrea gigas (Pacific oyster)), were examined. Tropomyosins were extracted from translucent and opaque portions of posterior adductor muscle, respectively, and cardiac muscle of each bivalve. There were two tropomyosin isoforms in the ark shell, the surf clam and the Pacific oyster. They were designated as TMa and TMb. In the ark shell, TMa was the common isoform and TMb was specific for the opaque portion of the adductor muscle. In the surf clam, TMb was the common isoform present in all tissues. TMa was found only in the translucent portion of muscle. In the Pacific oyster, TMb was the major component in both portions of adductor muscle and TMa was the major component in cardiac muscle, although both tropomyosins were included in all tissues. The mussel had only one tropomyosin.     

Microspectrophotometric characterization and localization of three visual pigments in the compound eye ofNotonecta glauca L. (Heteroptera)

Summary The absorption maxima ( _max) of the visual pigments in the ommatidia ofNotonecta glauca were found by measuring the difference spectra of single rhabdomeres after alternating illumination with two different adaptation wavelengths. All the peripheral rhabdomeres contain a pigment with an extinction maximum at 560 nm. This pigment is sensitive to red light up to wavelengths > 700 nm. In a given ommatidium in the dorsal region of the eye, the two central rhabdomeres both contain one of two pigments, either a pigment with an absorption maximum in the UV, at 345 nm, or — in neighboring rhabdoms — a pigment with an absorption maximum at 445 nm. In the ventral part of the eye only the pigment absorbing maximally in the UV was found in the central rhabdomeres. The spectral absorption properties of various types of screening-pigment granules were measured.     

Ultraviolet disinfection of Schistosoma mansoni cercariae in water

BackgroundSchistosomiasis is a parasitic disease that is transmitted by skin contact with waterborne schistosome cercariae. Mass drug administration with praziquantel is an effective control method, but it cannot prevent reinfection if contact with cercariae infested water continues. Providing safe water for contact activities such as laundry and bathing can help to reduce transmission. In this study we examine the direct effect of UV light on Schistosoma mansoni cercariae using ultraviolet light-emitting diodes (UV LEDs) and a low-pressure (LP) mercury arc discharge lamp.MethodologyS. mansoni cercariae were exposed to UV light at four peak wavelengths: 255 nm, 265 nm, 285 nm (UV LEDs), and 253.7 nm (LP lamp) using bench scale collimated beam apparatus. The UV fluence ranged from 0–300 mJ/cm² at each wavelength. Cercariae were studied under a stereo-microscope at 0, 60, and 180 minutes post-exposure and the viability of cercariae was determined by assessing their motility and morphology.ConclusionVery high UV fluences were required to kill S. mansoni cercariae, when compared to most other waterborne pathogens. At 265 nm a fluence of 247 mJ/cm² (95% confidence interval (CI): 234–261 mJ/cm²) was required to achieve a 1-log₁₀ reduction at 0 minutes post-exposure. Cercariae were visibly damaged at lower fluences, and the log reduction increased with time post-exposure at all wavelengths. Fluences of 127 mJ/cm² (95% CI: 111–146 mJ/cm²) and 99 mJ/cm² (95% CI: 85–113 mJ/cm²) were required to achieve a 1-log₁₀ reduction at 60 and 180 minutes post-exposure at 265 nm. At 0 minutes post-exposure 285 nm was slightly less effective, but there was no statistical difference between 265 nm and 285 nm after 60 minutes. The least effective wavelengths were 255 nm and 253.7 nm. Due to the high fluences required, UV disinfection is unlikely to be an energy- or cost-efficient water treatment method against schistosome cercariae when compared to other methods such as chlorination, unless it can be demonstrated that UV-damaged cercariae are non-infective using alternative assay methods or there are improvements in UV LED technology.     

Ultraviolet vision in birds: the importance of transparent eye media

Ultraviolet (UV)-sensitive visual pigments are widespread in the animal kingdom but many animals, for example primates, block UV light from reaching their retina by pigmented lenses. Birds have UV-sensitive (UVS) visual pigments with sensitivity maxima around 360–373 nm (UVS) or 402–426 nm (violet-sensitive, VS). We describe how these pigments are matched by the ocular media transmittance in 38 bird species. Birds with UVS pigments have ocular media that transmit more UV light (wavelength of 50% transmittance, λ_T0.5, 323 nm) than birds with VS pigments (λ_T0.5, 358 nm). Yet, visual models predict that colour discrimination in bright light is mostly dependent on the visual pigment (UVS or VS) and little on the ocular media. We hypothesize that the precise spectral tuning of the ocular media is mostly relevant for detecting weak UV signals, e.g. in dim hollow-nests of passerines and parrots. The correlation between eye size and UV transparency of the ocular media suggests little or no lens pigmentation. Therefore, only small birds gain the full advantage from shifting pigment sensitivity from VS to UVS. On the other hand, some birds with VS pigments have unexpectedly low UV transmission of the ocular media, probably because of UV blocking lens pigmentation.     

Melanin-Mediated Synthesis of Silver Nanoparticles and Their Affinity Towards Tyrosinase

The bacterial strain Pseudomonas sp. SSA has capacity to produce extracellular melanin that sequesters heavy metals. The brown-black melanin pigment was observed in the culture liquid and mediated synthesis of silver nanoparticles (AgNPs). The AgNPs were characterized using UV–visible, dynamic light scattering, energy dispersive X-ray, Fourier transform infrared and surface plasmon resonance spectroscopy, scanning electron and transmission electron microscopy and selected area electron diffraction analysis. The synthesized nanoparticles were found to be spherical in shape with size in the range of 14–30 nm and showed high antimicrobial activity against pathogenic bacteria and fungi. These nanoparticles revealed binding affinity towards fungal and human tyrosinases with K_D 4.601 × 10^–10 and 2.816 × 10^–5 M, respectively. In addition, produced nanoparticles did not show any toxic effect towards HeLa cells up to 20 μg/mL. These nanoparticles could find application in medicine and cosmetics due to their enzyme inhibition and antimicrobial activities.     

光谱法研究甲醇和盐酸对短梗霉黑色素的分离效果

应用紫外和红外光谱对甲醇和盐酸分离的短梗霉黑色素进行了分析。分析结果表明:甲醇和盐酸法分离的黑色素在紫外图谱215 nm处都有最大吸收峰,而甲醇法分离的黑色素其紫外图谱在260、280 nm处无吸收峰表明此法分离的黑色素不含核酸及蛋白质;红外图谱中,在3340 cm-1、1637 cm-1处有很强的吸收峰表现为黑色素的典型特征;同时在对照中发现盐酸多次处理后的黑色素显示较少的结构信息,说明盐酸沉降法有可能破坏黑色素的结构。由此选用甲醇作为沉淀剂有利于黑色素的纯化及确保其结构信息的完整,为进一步分析短梗霉黑色素的结构表征奠定了基础。     

Pigment Migration and Adaptation in the Eye of the Squid, Loligo pealei

The migration of the screening pigment was investigated in the retina of the intact squid. The action spectrum of pigment migration corresponds to the action spectrum of the visual pigment, rhodopsin, rather than to the absorption spectrum of the screening pigment. The total number of quanta required for a fixed criterion of pigment migration is the same, when the quanta are delivered over any period of time from 6 s to an hour or more. When less than 3–10% of the rhodopsin is isomerized, the screening pigment migrates out to the tips of the receptors with a time-course of 5–15 min, and back again over the same period of time. When rather more than 10% is isomerized, the outward migration takes 5–15 min, but the screening pigment does not migrate inwards, even after several hours in the dark. Indirect evidence suggests that the band of screening pigment, when it reaches the tips of the receptors, is approximately equivalent to a filter of 0.6 log units. The spectral sensitivity of the optic nerve response was measured, and was found to be broader than the absorption spectrum of squid rhodopsin in vitro; the broadness could be explained by self-screening, assuming a density of rhodopsin of 0.6 log units at 500 nm.     

The Spectral Sensitivities of Single Cells in the Median Ocellus of Limulus

The spectral sensitivities of single Limulus median ocellus photoreceptors have been determined from records of receptor potentials obtained using intracellular microelectrodes. One class of receptors, called UV cells (ultraviolet cells), depolarizes to near-UV light and is maximally sensitive at 360 nm; a Dartnall template fits the spectral sensitivity curve. A second class of receptors, called visible cells, depolarizes to visible light; the spectral sensitivity curve is fit by a Dartnall template with λ_max at 530 nm. Dark-adapted UV cells are about 2 log units more sensitive than dark-adapted visible cells. UV cells respond with a small hyperpolarization to visible light and the spectral sensitivity curve for this hyperpolarization peaks at 525–550 nm. Visible cells respond with a small hyperpolarization to UV light, and the spectral sensitivity curve for this response peaks at 350–375 nm. Rarely, a double-peaked (360 and 530 nm) spectral sensitivity curve is obtained; two photopigments are involved, as revealed by chromatic adaptation experiments. Thus there may be a small third class of receptor cells containing two photopigments.     

Estimation of protochlorophyll(ide) contents in plant extracts; re-evaluation of the molar absorption coefficient of protochlorophyll(ide)

In an attempt to solve the controversy about the evaluation of the molar absorption coefficient of PChl(ide), this coefficient is estimated in this work by using an original experimental approach. The calculated molar absorption coefficient of PChl(ide) is 30.4.10³ 1 mole^–1 cm^–1 at 626 nm in acetone 80%; it is close to that derived from the specific absorption coefficient of Koski and Smith when assuming that the pigment extracted by these authors was the esterified pigment: PChl. Sets of equations for the quantification of Chl(ide) a, Chl b and PChl(ide) in 80% acetone extracts are derived.Abbreviations PChl(ide) protochlorophyll(ide) - Chl(ide) chlorophyll(ide)     

Visible light accelerates the ultraviolet A‐induced degradation of eumelanin and pheomelanin

Exposure to excess ultraviolet (UV) A radiation induces the degradation/modification of both eumelanin and pheomelanin that may be deleterious to pigmented tissues. Although the spectral distribution of solar energy comprises nearly half of visible light (VL), few studies have been conducted to examine the role of VL in the photodegradation of both types of melanin, either VL alone or in combination with UVA. In this study, we examined the effects of physiological doses of VL (150 to 300 J cm^?2) alone or in combination with a physiological dose of UVA (20 J cm^?2) in normal human epidermal melanocytes. The degradation/modification of melanin structures was evaluated by our chemical degradation—high performance liquid chromatography methods. The results show that VL accelerates UVA‐induced changes in the structural features of both eumelanin and pheomelanin, although VL or UVA alone induced only minor changes in melanin structure. The differential spectral method provides support for the additive effects of VL.     

Electronic transition moments of 6-methyl isoxanthopterin—a fluorescent analogue of the nucleic acid base guanine

Fluorescent nucleic acid base analogues are important spectroscopic tools for understanding local structure and dynamics of DNA and RNA. We studied the orientations and magnitudes of the electric dipole transition moments (EDTMs) of 6-methyl isoxanthopterin (6-MI), a fluorescent analogue of guanine that has been particularly useful in biological studies. Using a combination of absorption spectroscopy, linear dichroism (LD) and quantum chemical calculations, we identified six electronic transitions that occur within the 25 000–50 000 cm⁻¹ spectral range. Our results indicate that the two experimentally observed lowest-energy transitions, which occur at 29 687 cm⁻¹ (337 nm) and 34 596 cm⁻¹ (289 nm), are each polarized within the plane of the 6-MI base. A third in-plane polarized transition is experimentally observed at 47 547 cm⁻¹ (210 nm). The theoretically predicted orientation of the lowest-energy transition moment agrees well with experiment. Based on these results, we constructed an exciton model to describe the absorption spectra of a 6-MI dinucleotide–substituted double-stranded DNA construct. This model is in good agreement with the experimental data. The orientations and intensities of the low-energy electronic transitions of 6-MI reported here should be useful for studying local conformations of DNA and RNA in biologically important complexes.     

酶法合成黑色素的稳定性研究

运用紫外分光光度计对以酪氨酸为底物酶法合成的黑色素进行稳定性分析,结果表明:该黑色素的最大吸收峰为212 nm,不溶于水和酸,易溶于碱,在碱性条件下颜色稳定。热、自然光、紫外光、蔗糖、葡萄糖对色素稳定性无影响;氧化剂H2O2和还原剂Na2SO3对其影响不大;几种金属离子(除Fe2+)对黑色素吸光值及颜色无影响。     

Risk of Eye Damage from the Wavelength-Dependent Biologically Effective UVB Spectrum Irradiances

A number of previous studies have discussed the risk of eye damage from broadband ultraviolet (UV) radiation. As the biologically damaging effectiveness of UV irradiation on the human body is known to be wavelength-dependent, it is necessary to study the distribution of the UV spectral irradiance. In order to quantify the ocular biologically effective UV (UVBE) irradiance exposure of different wavelengths and assess the risk of eye damage, UV exposure values were measured at Sanya, China (18.4° N, 109.7°E, altitude 18 m), using a manikin and a dual-detector spectrometer to measure simultaneously the ocular exposure and ambient UV spectral irradiance data and solar elevation angle (SEA) range (approximately 7°–85°). The present study uses the ocular UV spectral irradiance exposure weighted with the action spectra for photokeratitis, photoconjunctivitis and cataracts to calculate the ocular UVBE irradiance exposure for photokeratitis (UVBE_pker), photoconjunctivitis (UVBE_pcon) and cataracts (UVBE_cat). We found that the ocular exposure to UV irradiance is strongest in the 30°–60° SEA range when ∼50% of ocular exposure to UV irradiance on a summer’s day is received. In the 7°–30° SEA range, all the biologically highly effective wavelengths of UVBE_pker, UVBE_pcon and UVBE_cat irradiances are at 300 nm. However, in other SEA ranges the biologically highly effective wavelengths of UVBE_pker, UVBE_pcon and UVBE_cat irradiances are different, corresponding to 311 nm, 300 nm and 307 nm, respectively.     

Characterization of a Marine Bacterium Associated with Crassostrea virginica (the Eastern Oyster)

A gram-negative bacterium found to be closely associated with oysters has been isolated and characterized. The organism, designated LST, has a generation time of 106 min in Marine broth under optimal growth conditions at 25°C. During the decline phase of growth, it exhibits a morphological transition from a motile rod (ca. 1 μm in length) to an elongated, 3- to 40-μm, nonmotile, tightly coiled helix. LST synthesizes and releases a pigment in the stationary and decline phases of growth. Identified as melanin on the basis of chemical properties and UV absorbance maxima, the pigment comprises polymers of heterogeneous molecular weights, ranging from 12,000 to 120,000. The guanosine-plus-cytosine content of the LST DNA is 46%, and results of phenetic analysis and DNA-DNA hybridization indicate that this bacterium represents a new species. LST adheres to a variety of surfaces, including glass, plastics, and oyster shell, and has been shown to promote the settlement of oyster larvae.     

Cloning of cDNAs and hybridization analysis of lysozymes from two oyster species, Crassostrea gigas and Ostrea edulis

In bivalve molluscs including oysters, lysozymes play an important role in the host defense mechanisms against invading microbes. However, it remains unclear in which sites/cells the lysozyme genes are expressed and which subsequently produced the enzyme. This study cloned lysozyme cDNAs from the digestive organs of Pacific oyster Crassostrea gigas and European flat oyster Ostrea edulis. Both complete sequences of two oysters' lysozymes were composed of 137 amino acids. Two translated proteins present a high content in cysteine residues. Phylogenetic analyses showed that these oysters' lysozymes clustered with the invertebrate-type lysozymes of other bivalve species. In the Pacific oyster, lysozyme mRNA was expressed in all tissues except for those of the adductor muscle. In situ hybridization analyses revealed that lysozyme mRNA was expressed strongly in basophil cells in the digestive gland tubule of C. gigas, but not in digestive cells. Results indicated that the basophil cells of the oyster digestive gland are the sites of lysozyme synthesis.     

Self quenching of chlorosome chlorophylls in water and hexanol-saturated water

The optical properties of a methyl ester homolog of bacteriochlorophylld (BChld _M ) and bacteriochlorophyllc (BChlc) in H₂O, hexanol-saturated H₂O and methanol were studied by absorption, fluorescence emission, and circular dichroism (CD). In H₂O, BChld _M spontaneously forms an aggregate similar to that formed in hexane, with absorption maximum at 730 nm and fluorescence emission at 748 nm. For the pigment sample in hexanol-saturated H₂O, while the absorption peaks at 661 nm, only slightly red-shifted compared to the monomer, the fluorescence emission is highly quenched. When diluted 2–3 fold with H₂O, the absorption returns to around 720 nm, characteristic of an aggregate. The CD spectrum of the H₂O aggregate exhibits a derivative-shaped feature with positive and negative peaks, while the amplitude is lower than that of chlorosomes. The Fourier transform infrared spectra of BChld _M aggregates in H₂O and hexane were measured. A 1644 cm^–1 band, indicative of a bonded 13¹-keto group, is detected for both samples. A marker band for 5-coordinated Mg was observed at 1611 cm^–1 for the two samples as well. To study the kinetic behavior of the samples, both single-photon counting (SPC) fluorescence and transient absorption difference spectroscopic measurements were performed. For BChld _M in hexanol-saturated H₂O, a fast decay component with a lifetime of 10 to 14 ps was detected using the two different techniques. The fast decay could be explained by the concentration quenching phenomenon due to a high local pigment concentration. For the pigment sample in H₂O, SPC gave a 16 ps component, whereas global analysis of transient absorption data generated two fast components: 3.5 and 26 ps. The difference may arise from the different excitation intensities. With a much higher excitation in the latter measurements, other quenching processes, e.g. annihilation, might be introduced, giving the 3.5 ps component. Finally, atomic force microscopy was used to examine the ultrastructure of BChld _M in H₂O and hexanol-saturated H₂O. Pigment clusters with diameters ranging from 15 to 45 nm were observed in both samples.     

The role of a long-wavelength pigment form in the chlorophyll biosynthesis

Photoconversion of protochlorophyllide₆₅₀ form was observed in etiolated leaves illuminated with long-wavelength—690 nm—light. This process showed Shibata shift and was found to have a strong temperature dependence between 20 and –40°C. The low rate of reaction, the strong temperature dependence and calculations on the spectral overlap integral of absorption and fluorescence bands in this spectral region indicate that the phototransformation of the 650 nm form of protochlorophyllide may be caused by a back energy migration from a long-wavelength pigment form absorbing around 690 nm; this pigment form is probably a long-wavelength form of protochlorophyll/ide.     

Electroretinogram Characteristics and the Spectral Mechanisms of the Median Ocellus and the Lateral Eye in Limulus polyphemus

Electrical responses (ERG) to light flashes of various wavelengths and energies were obtained from the dorsal median ocellus and lateral compound eye of Limulus under dark and chromatic light adaptation. Spectral mechanisms were studied by analyzing (a) response waveforms, e.g. response area, rise, and fall times as functions of amplitude, (b) slopes of amplitude-energy functions, and (c) spectral sensitivity functions obtained by the criterion amplitude method. The data for a single spectral mechanism in the lateral eye are (a) response waveforms independent of wavelength, (b) same slope for response-energy functions at all wavelengths, (c) a spectral sensitivity function with a single maximum near 520 mµ, and (d) spectral sensitivity invariance in chromatic adaptation experiments. The data for two spectral mechanisms in the median ocellus are (a) two waveform characteristics depending on wavelength, (b) slopes of response-energy functions steeper for short than for long wavelengths, (c) two spectral sensitivity peaks (360 and 530–535 mµ) when dark-adapted, and (d) selective depression of either spectral sensitivity peak by appropriate chromatic adaptation. The ocellus is 200–320 times more sensitive to UV than to visible light. Both UV and green spectral sensitivity curves agree with Dartnall's nomogram. The hypothesis is favored that the ocellus contains two visual pigments each in a different type of receptor, rather than (a) various absorption bands of a single visual pigment, (b) single visual pigment and a chromatic mask, or (c) fluorescence. With long duration light stimuli a steady-state level followed the transient peak in the ERG from both types of eyes.