MICELLE FORMATION IN MIXTURES OF ANIONIC AND NONIONIC SURFACTANTS

The critical micelle concentration of mixtures of anionic and nonionic surfactants was measured. The anionic surfactants were alkylbenzene sulfonates and the nonionic surfactants were polyoxyethylene nonylphenols and a polyoxy-ethylene alcohol. The effect of added electrolyte, the number of ethylene oxide units in the polyethoxylate, and the anionic alkyl chain length were studied. All systems showed substantial negative deviations (lower CMC) from ideal solution theory. The results can be represented by regular solution theory. Charge separation appears to be the source of the nonideality. This considers the reduction of electrostatic repulsion between the ionic surfactant head groups in the mixed micelle, due to the insertion of nonionic hydrophilic groups between these charged groups, to be the cause of enhanced micelle formation. The physical basis of regular solution theory was shown to be consistent with the charge separation effect.     

ORIENTATION OF RETINYLIDENE CHROMOPHORE OF HYPSORHODOPSIN IN FROG RETINA

Abstract— Hypsorhodopsin and bathorhodopsin were formed in the frog retina by irradiating rhodopsin at liquid He temperature (9 K) with orange light (> 520 nm) and blue light (437 nm), respectively. Hypsorhodopsin was converted to bathorhodopsin in the retina by warming above 32 K in the dark. Similar phenomena were observed in the rod outer segment suspension. A difference spectrum between hypsorhodopsin and bathorhodopsin in the retina produced by warming was almost identical with that in the rod outer segment suspension. This suggests that the transition dipole moment of hypsorhodopsin is parallel to the disk membrane plane which is also parallel to that of bathorhodopsin.     

SUBSTITUTION OF RETINAL BY ANALOGUES IN RETINAL PIGMENTS OF HALOBACTERIUM HALOBIUM. CONTRIBUTION OF BACTERIORHODOPSIN AND HALORHODOPSIN TO PHOTOSENSORY ACTIVITY

Abstract— In Halobacrerium hnlobium. retinal is the chromophore of the light-energy converting pigments bacteriorhodopsin (BR) and halorhodopsin (HR) and of the sensory photosystems. PS 370 and PS 565. In both photosystems as well as in BR and HR. retinal was substituted by retinal analogues. Retinal₂ ( 3,4-dehydro-retinal ) . shifts the main sensitivity maximum of PS 370 and of PS 565 by about 1.5 nm to longer wavelengths. The absorption maxima of BR and HR are both shifted in the same direction, but by 37 nm. 13-Ethylretinal and 13-propylretirnal shift the main sensitivity maximum of each sensory photosystem to shorter wavclengths; the absorption maxima of BR and HR are shifted in the same direction but to a smaller extent. Both sensory photosystems are equally active with retinal and with each of the three analogues as the chromophore. After substitution of retinal by the analogues, the action spectra of PS 565 of the BR-containing strain R₁L₃ show a secondary bensitivity peak in addition to the main peak. This secondary peak matches the absorption maximum of the corresponding BR. In the action spectra of the BR-deficient strainET–15 this secondary peak is missing. Action spectra of PS 565 of the BR-deficient strainL–33, which synthesizes increased amounts of HR. with all retinals show a secondary peak which matches the absorption maximum of the corresponding HR.
The results show that the analogues can substitute retinal in both sensory pigments as well as in BR and HR. Moreover, the data support the previous assumption that both BRand HR, although not required for photosensory activity can contribute to photosensing through PS 565.     

全氟辛酸与十二烷基硫酸钠混合溶液中的胶团形成

用表面张力法、电导法,pH测定法研究全氟辛酸-十二烷基硫酸钠混合水溶液的胶团形成及全氟辛酸胶团的特性.结果表明:(1)电导法与pH测定法弥补了表面张力法的不足,进一步证明在碳氟链表面活性剂与碳氢链表面活性剂混合水溶液中形成两种胶团.(2)全氟辛酸与十二烷基硫酸钠混合水溶液中所形成的两种胶团,分别基本上由全氟辛酸和十二烷基硫酸钠组成.十二烷基硫酸钠的存在对全氟辛酸胶团的形成不显示影响.全氟辛酸的氢离子对十二烷基硫酸钠胶团显示反离子效应.(3)全氟辛酸是典型的离子型表面活性剂,由于它对氢离子的结合力特别强,其胶团几乎是电中性的.这一特性可以解释全氟辛酸-十二皖基硫酸钠混合溶液胶团形成的机制.     

A POSSIBLE MECHANISM FOR THE ROLE OF N-RETINYLIDENE PHOSPHATIDYL ETHANOLAMINE IN THE REGENERATION OF RHODOPSIN

Abstract— A series of molecular orbital calculations on a model Schiff base comparable to protonated N -retinylidene phosphatidyl ethanolamine isomers has been made. The effect of the charged oxygen atoms of the phosphate moiety on the distribution of positive charge along the polyene chain of these isomers has been calculated. The stabilizing coulombic energy of interaction of these opposite charges and the possibility of free rotation around carbonxarbon double bonds in the electronically excited state has led to the conclusion that an 11- cis Schiff base isomer is the most probable product of the photoisomerization of an all-trans Schiff base.
The formation of a stable unprotonated all-trans Schiff base in aqueous detergent dispersion and its subsequent conversion to the protonated form, both with absorption spectra in conformity with the literature, is demonstrated.     

LOW TEMPERATURE FTIR STUDIES OF THE PROTONATION OF A RETINYLIDENE SCHIFF BASE

Abstract— This note supplements the paper by Badilescu et al. (1989) [ Photochem. Photobiol. 49 , 313-318]. Low temperature solution spectra of 1: 2 and 2: 1 mixtures of trans -retinylidene-tertbutylamine and propanoic acid are presented. The results show that the degree of protonation is both temperature and concentration dependent.     

粘度法研究壳聚糖与两性聚氨酯胶束间的相互作用

通过粘度法考察了壳聚糖(CS)在盐酸水溶液中与表面带有正电荷的两性聚氨酯(APU)胶束的相互作用，并研究了小分子盐浓度、pH及不同混合方式对复合体系粘度的影响．结果表明：在壳聚糖／APU盐酸混合体系中，较高浓度下APU胶束与壳聚糖分子间的静电斥力作用导致壳聚糖大分子链的伸展，使体系粘度提高，同时降低了壳聚糖溶液对电解质、pH的敏感性；不同混合过程导致壳聚糖大分子构像及其与APU组装、复合形态有很大差别，使混合体系流变性表现出明显的不同．     

分子在胶团溶液中分布的研究

胶团溶液的应用非常广泛,而客体分子在胶团溶液中的溶解分布则是一个很重要的参数。通过研究客体分子在胶团溶液中的平衡分布,还可得到关于客体分子与胶团之间相互作用的重要信息。本文用稳态荧光方法研究了香豆素衍生物(C47,C311和C120)在溴代十二烷基三甲铵(C_(12)TAB)和溴代十六烷基三甲铵(C_(16)TAB)胶团溶液中的荧光光谱特性,研究和测定了这些染料在胶团溶液中的分布常数。     

ABSORPTION SPECTRA OF TCA-DENATURED RHODOPSIN AND OF A SCHIFF BASE COMPOUND OF RETINAL

Abstract— When TCA-denatured rhodopsin was frozen in liquid nitrogen, Λ_max was markedly shifted to longer wavelengths as the concentration of TCA increased. After TCA denaturation, species specific absorption disappeared and the absorption maxima of the squid pigments became identical with those of corresponding pigments of octopus.
In solutions at 5° the bathochromic shift of Λ_max of TCA denatured rhodopsin was observed at higher concentrations of TCA than in the frozen state. Λ_max of N-retinylidene-butylamine (NRB) was also displaced towards longer wavelengths with increasing concentrations of TCA. This bathochromic shift was enhanced by freezing. The mode of the bathochromic shift of Λ_max provoked by TCA was very similar both in the cases of denatured rhodopsin and of NRB. The absorption spectrum of NRB was identical in shape with that of TCA-denatured rhodopsin, as the half-band widths of both materials were about 5500 cm^-1 in the liquid state and 5000 cm^-1 in the frozen state. Λ_max of retinal and NRB were red shifted in polar and polarizable solvents.
It was concluded that the strong acidity and the relatively large polarizability of TCA are responsible for the bathochromic shift of Λ_max of the Schiff base in TCA-denatured rhodopsin.     

COMPARISON OF THE PATHWAYS AND QUANTUM YIELDS OF DIRECT PHOTOISOMERIZATION OF UNPROTONATED AND PROTONATED N-BUTYLAMINE SCHIFF BASES OF ISOMERIC RETINYLIDENEACETALDEHYDE WITH THOSE OF SCHIFF BASES OF ISOMERIC RETINAL: RATIONALIZATION OF THE SELECTION OF THE RETINYLIDENE CHROMOPHORE BY RETINOCHROME

Abstract— The pathways and quantum yields of direct photoisomerization of unprotonated and pro-tonated n-butylamine Schiff bases (SB and PSB) of isomeric retinylideneacetaldehyde (C22 aldehyde) were determined in n-hexane, acetonitrile and methanol for the former and in acetonitrile and methanol for the latter. The results are compared with those of the Schiff bases of isomeric retinal (C20 SB and C20 PSB) reported previously (Koyama et al., Photochem. Photobiol. 54 , 433–443, 1991). The isomerization pathways and quantum yields of C22 SB are more or less similar to those of C20 SB, but conspicuous differences in the isomerization pathways are found between C22 PSB and C20 PSB. The homogeneous (exclusive) isomerization of the retinylidene chromophore from all-trum to 11-cis in retinochrome is rationalized not by C22 PSB but by C20 PSB.
Almost complete one-way isomerization from cis to trans of C22 SB (in n-hexane) is ascribed to isomerization via the T₁ state, while mutual isomeritation between cis and tram of C22 PSB is ascribed to isomerization via the S₁ (B_u) state. The T_I potential of C22 SB and the S₁ potential of C22 PSB are discussed based on photostationary state compositions.     

TRIPLET STATES AND cis-trans PHOTOISOMERIZATION PROCESSES IN THE SCHIFF BASES OF RETINAL ISOMERS

Abstract —The triplet states of the n -butyl-amine Schiff bases of 11- cis , 9- cis , 13- cis and all- trans retinal are produced via triplet-triplet energy transfer. Their absorption spectra, peaking around 435 nm, and their decay kinetics are recorded using pulsed-laser photolysis. Direct-excitation (φ^D_ISO) and triplet-sensitized (φ^T_ISO) photoisomerization yields, determined using steady irradiation methods, are found to be: φ^T_ISO (9- cis ) = 0.06, φ^T_ISO (11- cis ) = 045, φ^T_ISO (13- cis ) = 008, φ^T_ISO (all- trans ) = 0.02-0.05, φ^D_ISO (11- cis , = (4 ± 1) × 10^-3, φ^D_ISO (all- trans ) = (2 ± 1) × 10^-3. The possible role of the triplet state in the isomerization of rhodospin is discussed.     

PICOSECOND AND NANOSECOND TSOMERIZATION KINETICS OF PROTONATED 11-CIS RETINYLIDENE SCHIFF BASES

Abstract— Picosecond and nonosecond spectroscopy has been used to study the isomerization mechanism of protonated 11- cis retinylidene Schiff bases. The formation and bleaching of absorption bands within 10 ps and corresponding decay and recovery within 11 ns indicate that the isomerization mechanism of the protonated Schiff bases is not identical to rhodopsin in which the primary photophysical event is probably due to electron transfer or partial isomerization of the chromophore to a nonplanar conformation.     

ENERGETICS OF PROTONATION-DEPROTONATION OF THE CHROMOPHORE IN RETINAL PROTEINS

Abstract— We investigate the energetics of protonation and deprotonation of retinylidene Schiff-base (SB) which is realized in the functioning of retinal proteins. We first calculate the energy difference ΔE between the protonated and unprotonated states of the SB by the ab initio molecular orbital method, using two kinds of molecular model; a counter-ion model where a carboxyl group of Glu or Asp is directly hydrogen-bonded to the SB, and a water-bridge model where a water molecule bridges the carboxyl group and the SB. The calculated results indicate that the protonated SB state is unstable compared with the unprotonated SB state in either model. In addition, we find that coordination of some water molecules to the carboxyl group reduces ΔE significantly. The value of AE for the counterion model with two coordinated water molecules is 0.003 eV. Next, we calculate the electrostatic interaction energy between a tryptophan residue and the SB. We find that the protonated state is more stabilized than the unprotonated state by about 0.1 eV with one tryptophan residue. This fact indicates that if some aromatic amino acid residues work cooperatively, they can contribute to significantly reducing ΔE. We also discuss the possible role of amino acid residues which make hydrogen-bond with the carboxyl group of interest.     

ISOMERIZATION OF THE RETINYLIDENE CHROMOPHORE OF BACTERIORHODOPSIN IN LIGHT ADAPTATION: INTRINSIC ISOMERIZATION OF THE CHROMOPHORE AND ITS CONTROL BY THE APO-PROTEIN

Abstract— The dependence of the isomeric configuration of the retinylidene chromophore of bacteriorhodopsin on the pH value and on the wavelength of irradiation (in a photostationary state) were examined by high performance liquid chromatographic analyses of extracted retinal. The process of isomerization of the chromophore during light adaptation was also traced. More than 93% of all- trans and less than 5% of 13- cis retinal were extracted in the photostationary state for irradiation at 560 nm in the pH region of5–9 as well as for irradiation in the wavelength region of 400–650 nm at pH 7. Comparison of the above photostationary state composition with that of protonated n -butylamine Schiff base of retinal indicates that strong constraint is applied to the chromophore by the apo-protein. The constraint can be changed at low or high pH by a partial denaturation or transition of the apo-protein, which results in the generation of 11- cis retinal in the extract. At higher photon density, the isomerization process of the chromophore during light adaptation at pH 7 was characterized, as extracted isomeric retinal, by (1) the initial decrease in 13- cis and increase in all- trans , (2) a subsequent, transient toward the above photostationary state composition. The results are discussed in terms of both the photoisomerization pattern inherent in the retinylidene chromophore and the control by the apo-protein.     

REACTION OF RETINOL AND RETINAL WITH SINGLET OXYGEN

Abstract— The rate constants for the reactions of all- trans retinol and retinal with singlet oxygen were measured in a variety of solvents of different polarities. The rate constants increased with increasing solvent dielectric constant, which suggests that a charge transfer mechanism plays a part in the reaction. Further, the rate constant of reaction of singlet oxygen with retinal is greater than that with retinol. Since retinal has a lower ionization potential than retinol, these relative rates also support the hypothesis of charge transfer involvement in the reaction.     

BATHOCHROMICITY OF RETINAL SCHIFF BASES IN CELLULOSE MATRIX

Abstract Schiff bases of all-trans-retinal (formed with n-butylamine, tryptamine and β-naphthylamine) and of benzaldehyde, trans -cinnamaldehyde and all- trans -retinal with aniline exhibit an appreciable red shift in their UV-visible maxima on intercalation in cellulose matrix relative to their absorption in solution in the absence of acid. Treatment of these model compounds with trichloroacetic acid in solution gives the corresponding protonated salts. The red shift due to the cellulose environment is, however, less than the red shift in acid solutions. However, an exception is all- trans-N -retinylidenetryptamine for which the red shift in cellulose is quite close to the corresponding value for the protonated salt in heptane and methanol. N -Benzalideneaniline and trans- N -cinnamalideneaniline, with shorter polyenic moieties, tend to show a greater bathochromic shift in cellulose. all-trans- N -Retinylidene- n -butylamine, all- trans-N -retinylidenetryptamine and all- trans-N -retinylidene-β-naphthylamine show a reduced bathochromic shift when intercalated in cellulose pretreated with a base such as n -butylamine. The chromophore of all- trans-N -retinylidenetryptamine is stabilized by the presence of the indole moiety. These results indicate the importance of hydrogen-bond interactions at the chromophore sites of rhodopsins. A mechanistic proposal for explaining protonation, stability and wavelength regulation in the opsin family of proteins is discussed.