Mirror Image Relationship Research Articles

Mesoscale decrease of surface phosphate and associated phytoplankton dynamics in the vicinity of the subtropical South Pacific islands

Surface distributions of nutrients and phytoplankton were investigated in the vicinity of the subtropical South Pacific islands by using a continuous underway system with a highly sensitive nutrient analysis. A total of 17 transects, whose lengths ranged between 42 and 271 km, were sampled for continuous nutrient measurements. The study area was characterized by an overall depletion of nitrate+nitrite (<15 nM), but phosphate varied from 7 to 192 nM. The transects were grouped into 4 patterns according to distribution of phosphate concentrations. In 7 transects, a mesoscale decrease in phosphate occurred, coinciding with an elevation of in vivo chlorophyll fluorescence, which was accompanied by an increase in phytoplankton abundance as revealed by microscopy, flow cytometry, and accessory pigments. This mirror–image relationship between the phosphate concentration and phytoplankton abundance was most apparent on both a 99-km transect east of Tonga, where the phosphate concentration ranged from 17 to 125 nM, and on a 98-km transect west of Fiji, where the phosphate concentration ranged from 23 to 136 nM. Both these transects contained distinct blooms of Trichodesmium in areas with the lowest concentrations of phosphate. In other 2 transects, fluctuations in phosphate concentrations showed no distinct relationship with chlorophyll fluorescence. Other patterns that emerged included consistently high concentrations, ranging from 109 to 192 nM, in 5 transects and consistently low phosphate concentrations, ranging from 7 to 50 nM, in 3 transects. Abundance of Trichodesmium, Prochlorococcus, Synechococcus, and all accessory pigments examined tended to be higher in the low phosphate transects than in the high phosphate ones. In particular, Trichodesmium occurred in low phosphate water (<25 nM). There was no significant relationship between phosphate concentrations and nanoplanktonic unicellular cyanobacteria. Our observations suggest that surface phosphate decreases are associated with phytoplankton utilization of phosphate, and that nitrogen supply from Trichodesmium may contributes to this utilization.

Conformational study of chiral penicillamine ligand on optically active silver nanoclusters with IR and VCD spectroscopy

Abstract The conformation of chiral d -/ l -penicillamine ( d -/ l -Pen) adsorbed on optically active silver nanoclusters with a mean core diameter of about 1.1 nm was investigated by infrared (IR) and vibrational circular dichroism (VCD) spectroscopy. IR spectra of the d -/ l -Pen-protected nanoclusters in D2O/CD3OD solution are essentially identical, but the VCD exhibits a mirror image relationship indicating that these species have enantiomeric relationship. The experimental IR and VCD spectra are compared with the calculated ones for different model conformers at the DFT/B3PW91 level. The analysis in the spectral region of νasym(COO−) and δsym(NH2) modes reveals significant shortcomings when comparing with vacuum calculations. We then take a bulk solvent effect into account in the theoretical calculations to obtain better agreement, resulting in the establishment of a preferential conformation of chiral penicillamine on the silver nanocluster surface.

Nanosecond spectroscopy of retinol bound to proteins

Nanosecond fluorescence techniques have been employed for studying the mode of binding of retinol to the retinol binding protein (RBP), β-lactoglobulin, and human serum albumin. A substantial increase in the fluorescence decay time of bound retinol relative to that in hexane is attributed to a change in its conformation upon binding. It is demonstrated that retinol bound to RBP and to β-lactoglobulin lacks flexibility in the nanosecond scale. The latter protein, which is shown to be globular, induces the appearance of structure in the absorption spectrum of the ligand but not in its fluorescence spectrum. It is demonstrated that the mirror-image relationship between the modified absorption and fluorescence spectra of retinol bound to this protein breaks down. This implies the existence of a profound difference between the nuclear configurations of the ground and excited singlet electronic states of bound retinol.

π-Electron systems: Recent developments in electronic spectroscopy and the PPP model

The PPP model gives good account of the recently measured MCD signs and polarizations of ππ* transitions in hydrocarbons. The previously predicted mirror-image relation between the MCD spectra of two species paired in the sense of alternant symmetry has now been verified experimentally. Consideration of pairing properties suggests a classification of π-electron chromophores into “hard,” whose MCD sign pattern is intrinsic and little affected by substituents, and “soft” (those paired with themselves), whose MCD sign pattern is dominated by the substituents and heteroatoms present. In many instances, prediction of the substituent-induced signs requires no more than an inspection of the Hückel orbitals of the parent hydrocarbon. Agreement with experiment is very good for low-energy transitions.

Rare Earth Elements in Manganese Nodules from the Central Pacific Ocean

Abstract Manganese nodules in areas CP and CC of the central Pacific are rich in REE. Comparatively speaking, the REE contents of nodules in area CP are hihger than those in area CC; and the REE contents of nodules from seamounts are higher than those of nodules from sea-floor plains and hills. Within the nodules, the REE show a zonal distribution. The REE distribution patterns of the nodules are similar to those of the sediments and have a mirror image relationship with those of the sea water. Trivalent REE were not obviously differentiated when they entered into the nodules from the sea water. A major factor causing the difference of REE abundances between nodules and sediments is the redox conditions. The redox intensity of the ocean floor of the Pacific is controlled mainly by Antarctic Bottom Water (AABW). The iron-bearing facies in the nodules is the main carrier of REE.

Rare Earth Elements in Manganese Nodules from the Central Pacific Ocean

Abstract Manganese nodules in areas CP and CC of the central Pacific are rich in REE. Comparatively speaking, the REE contents of nodules in area CP are hihger than those in area CC; and the REE contents of nodules from seamounts are higher than those of nodules from sea-floor plains and hills. Within the nodules, the REE show a zonal distribution. The REE distribution patterns of the nodules are similar to those of the sediments and have a mirror image relationship with those of the sea water. Trivalent REE were not obviously differentiated when they entered into the nodules from the sea water. A major factor causing the difference of REE abundances between nodules and sediments is the redox conditions. The redox intensity of the ocean floor of the Pacific is controlled mainly by Antarctic Bottom Water (AABW). The iron-bearing facies in the nodules is the main carrier of REE.

Scanning Electron Microscopy Measurements of the Surface Roughness of Paper

A new approach to the measurement of x−y uniformity of the surface of a paper sheet is described. Scanning electron micrographs are taken of both the top and bottom surfaces of a paper sheet and image-analyzed. The images were converted to grayscale, and the standard deviation of the pixel brightness was called the “SEM roughness index” and calculated for each surface. Both commercial newsprint sheets and handsheets made with kraft, TMP, and recycled fibers were examined. Debonders and cationic polymers were added to some sheets. The addition of debonders increases the index on the top side of the sheet but decreases it on the bottom. This is caused by the movement of fines from the top to the bottom side. The addition of cationic polymers increases the SEM roughness index by increasing the degree of microfloc formation. Samples taken across a reel from a commercial paper machine tend to show a mirror image relationship between the top and bottom surfaces. The SEM roughness index is able to detect subtle changes in sheet structure caused by differences in the mode of addition of polymers used for retaining fines in the sheet.

Linear and nonlinear optical spectroscopic characterisation of triphenylamine and 1,2,3-tris(3-methylphenylphenylamino)benzene

The molecule triphenylamine (TPA) in tetrahydrofuran (THF) and the starburst triphenylamine oligomer 1,3,5-tris(3-methylphenylphenylamino)benzene (m-MTDAB) in THF and as neat film are characterized. Absorption and emission spectroscopic parameters are determined. The S 0–S 1 transition is found to be weak (nπ * transition) with small fluorescence quantum yield and efficient non-radiative decay (singlet–triplet intersystem crossing). The S 0–S 1 absorption cross-section spectra in the tails of the broad first absorption bands of the compounds are separated out by radiative lifetime determination and applying the mirror-image relation between absorption and emission. Excimer formation is observed for m-MTDAB neat films, its photo-dynamics is studied, and monomer and excimer stimulated emission cross-section spectra are extracted. Reverse saturable absorption is observed for TPA and m-MTDAB in picosecond laser nonlinear transmission measurements (laser duration 35 ps, laser wavelength 347.15 nm) and the responsible excited-state absorption cross-sections are determined. A new method is developed to calculate the excited-state absorption cross-section spectra of the samples in the fluorescence spectral region by amplification/attenuation of spontaneous emission measurements. The excited-state absorption is found to be larger than the stimulated emission for TPA in THF and for m-MTDAB films excluding their lasing ability. For m-MTDAB in THF the stimulated emission is found to be slightly larger than the excited-state absorption at the wavelength position of peak fluorescence emission.

Chiral Functionalization of Optically Inactive Monolayer-Protected Silver Nanoclusters by Chiral Ligand-Exchange Reactions

We report the ligand-exchange reaction between the optically inactive racemic penicillamine monolayer on a silver nanocluster surface and enantiopure D- or L-penicillamine dissolved in solution. Emergence of the identical band positions in the gel electrophoresis separation assures the presence of size-invariant silver nanoclusters (1.05 and 1.30 nm in core diameter) during the ligand-exchange reaction and allows us to further examine the optical/chiroptical properties of these nanoclusters. Consequently, chiral functionalization of the achiral silver nanoclusters has been demonstrated, yielding large Cotton effects in metal-based electronic transitions with an almost mirror-image relationship between the enantiomeric compounds. The ligand-exchange experiments as well as the normal syntheses of the silver nanoclusters revealed that their absorption profiles and anisotropy factors were strongly dependent on the enantiomeric purity (or enantiomeric excess) of surface chiral penicillamine, so that (several-fold) larger chiroptical responses of the silver nanoclusters as compared to those of the analogous gold clusters with a comparable size could be induced by the metal core deformation or rearrangement along with a universally influential vicinal contribution from the chiral ligand field.

Chiroptical Responses of d-/l-Penicillamine-Capped Gold Clusters under Perturbations of Temperature Change and Phase Transfer

We report chiroptical properties of optically active d-/l-penicillamine-capped gold clusters as a function of temperature or dispersion phase. The clusters examined are size-selected via gel electrophoresis. Circular dichroism (CD) signals of the gold clusters (0.57 nm in the core diameter), whose sizes have been determined by a small-angle X-ray scattering (SAXS) analysis, are practically temperature-dependent (20 and 40 °C), whereas ordinary absorption spectra are almost independent of the temperature. Furthermore, phase transfer of the gold clusters (0.57 nm) from water to toluene is successfully achieved by hydrophobization using ion association between tetraoctylammonium cations and carboxylate anions in surface penicillamine molecules. The phase-transferred clusters covered with d- or l-enantiomer still display intense optical activity with the opposite sign (mirror-image relationship) in the metal-based electronic transition region. Upon phase transfer, we find a significant change in the profiles of the anisotropy factor. On the basis of these temperature- and phase-dependent chiroptical behaviors of the gold clusters, we discuss the origins of their optical activity in the context of a dissymmetric field model.

Synthesis and Chiroptical Study of d/l-Penicillamine-Capped Silver Nanoclusters

We report the synthesis and chiroptical properties of silver nanocluster enantiomers. The surface of the silver nanoclusters is covered with l/d-penicillamine or their racemate. The clusters are separated by gel electrophoresis according to their charge and size into well-defined compounds. The mean core diameter of each fractioned component varies from 1 to 3 nm. The separated compounds of silver nanoclusters covered with l- or d-form thiol show strong optical activity or circular dichroism with opposite sign (mirror image relationship) in the metal-based electronic transitions (obtained anisotropy factor is on the order of 1 × 10-3 to 1 × 10-5), suggesting that the nanoclusters have well-defined stereostructures as common chiral molecules do. With a decrease in the mean cluster diameter, the anisotropy factor gradually increases at first, but a steep rise is observed when the diameter becomes smaller than ∼1.5 nm. The chiroptical response of the silver nanoclusters is consequently several-fold larger th...

On the excitation wavelength dependence of the fluorescence of bacteriorhodopsin

We present a systematic study of the time-integrated fluorescence of native bacteriorhodopsin, as a function of excitation wavelength across the visible absorption band. While the fluorescence maximum is unaffected, the spectrum broadens on the high-energy side, with decreasing excitation wavelengths. In addition, there is no mirror image relation between emission and absorption, even for the longest excitation wavelengths. By comparison with the retinal cation in solution, we attribute these observations to vibrationally hot emission, and to the topology of the excited state surface on the way to isomerization.

Mirror-image relations in category learning

The discrimination of patterns that are mirror-symmetric counterparts of each other is difficult and requires substantial training. We explored whether mirror-image discrimination during expertise acquisition is based on associative learning strategies or involves a representational shift towards configural pattern descriptions that permit resolution of symmetry relations. Subjects were trained to discriminate between sets of unfamiliar grey-level patterns in two conditions, which either required the separation of mirror images or not. Both groups were subsequently tested in a 4-class category-learning task employing the same set of stimuli. The results show that subjects who had successfully learned to discriminate between mirror-symmetric counterparts were distinctly faster in the categorization task, indicating a transfer of conceptual knowledge between the two tasks. Additional computer simulations suggest that the development of such symmetry concepts involves the construction of configural, protoholistic descriptions, in which positions of pattern parts are encoded relative to a spatial frame of reference.

Chiral dioxovanadium(V) complexes with single condensation products of 1,2-diaminocyclohexane and aromatic o-hydroxycarbonyl compounds: Synthesis, characterization, catalytic properties and structure

New dioxovanadium(V) complexes bearing tridentate products of single condensation of RR(−) and of SS(+)-1,2-diaminocyclohexane with salicylaldehyde and its derivatives, 2-hydroxy-1-naphthaldehyde and 1-hydroxy-2-acetonaphthone, have been synthesized. The crystal structure of the {RR(−)-1-amino-2-N-[1′-(1″-oxido-κO-2″-naphthyl)ethylidene]aminocyclohexane-κ2N}dioxovanadium(V) hemihydrate hemiethanol solvate, determined by X-ray analysis, is characterized by trigonal bipyramidal coordination geometry of complex molecules which are linked to solvent molecules by hydrogen bonds to form chains. The cyclohexane ring is in chair conformation with a very small distortion towards half-chair and envelope forms. Complexes were characterized by UV–Vis, FTIR, 1H, 13C, 51V NMR and CD spectroscopies. CD spectra of {RR(−)-1-amino-2-N-[(2′-oxido-κO-5′-nitrophenyl)methylene]aminocyclohexane-κ2N}dioxovanadium(V) and of R(−)-1,2-diaminopropane analogue do not bear mirror image relationship in contrast to V(IV and V), Cu(II) and Ni(II) complexes containing double condensed diamines in the same absolute configurations. 1H and 13C NMR resonance signals of all complexes dissolved in DMSO were assigned. The complexes bearing the methoxy substituent in position 3 or 5 of the aryl group catalyse the oxidation of methyl phenyl sulfide by cumene hydroperoxide to the corresponding sulfoxide with reasonable enantiomeric excesses (19–23%).

Comprehensive Geological and Geophysical Study in Middle Southern Region of China

AbstractWe use gravity, magnetic and earthquake data to carry out a comprehensive geological and geophysical study in the middle southern region of China. According to the distribution of gravity and magnetic anomalies, four gravity anomalous zones and three magnetic anomalous zones are identified. According to calculations of gravity data, the crustal thickness ranges between 29.5 and 41 km with a general trend of being thick in the west and thin in the east. There is a mirror image relationship between crust thickness and terrain relief. According to magnetic data, the depth of Curie interface ranges between 12 and 40 km in the study area. The crust of study region is divided into four layers by velocity interfaces at 3, 13, 23 and 36km, and below the crust two velocity interfaces at 71 and 120km are adopted in seismic tomographic study. Tomographic imaging result indicates that velocity distribution generally reflects the characteristics of crisscrossed fault blocks. Longitudinally, the upper crust structure in Jianghan–Dongting basins and their marginal orogenic belts does not change much, the middle and lower crust were generally transformed by modern tectonic activities, leading to certain changes in lithospheric structure. Their main presentation is the enlargement of low velocity areas, it is particularly so in the lower part of the crust. This is closely related to the tension of depressive basins and lithospheric intrusion in orogenic belt. Analysis and calculations of geophysical fields reveal 34 principal fault zones in the study area. According to geotectonic theory of lithospheric plate, as well as the variations of deep‐seated structures of lithosphere, crustal structure and crystalline basement, the different tectonic units‐massives in the study area can be taken as primary tectonic units. The deep grand fault zones among them can be taken as the boundary zones. In light of this principle, two primary tectonic units and five secondary tectonic units are identified.

Biomolecular mirror‐image recognition: Reciprocal chiral‐specific DNA binding of synthetic enantiomers of zinc finger domain from GAGA factor

To experimentally demonstrate the mirror-image recognition in protein and DNA interaction, we have designed a small DNA-binding peptide based on the zinc-finger domain of GAGA transcription factor. Circular dichroism data suggest that the conformations of peptide enantiomers as well as the DNA enantiomers have a mirror-image relationship. The gel mobility shift assay showed that the synthetic enantiomers of the peptide showed reciprocal chiral-specific interactions with the DNA; the natural L-peptide binds specifically with the natural D-DNA substrate, and the unnatural D-peptide binds specifically with the unnatural L-DNA substrate. The present data imply that the folding of the L- and D-enantiomers of the peptide as well as the DNA substrates are exact mirror images of each other in 3-D structure and biological activity, and generalize the chiral-specific nature of biomolecular interaction.

Large Optical Activity of Gold Nanocluster Enantiomers Induced by a Pair of Optically Active Penicillamines

We have succeeded for the first time in preparing a pair of gold nanocluster enantiomers protected by optically active thiols: D- and L-penicillamine (D-Pen and L-Pen). Circular dichroism (CD) spectroscopy confirmed the mirror image relationship between the D-Pen-capped and the L-Pen-capped gold nanoclusters, suggesting that the surface modifier acts as a chiral selector, and that the nanoclusters have well-defined stereostructures as common chiral molecules do. No CD signals could be obtained when the gold nanoclusters were synthesized by using a racemic mixture (rac-Pen). These chiroptical properties were investigated for the three separated fractions of each of the gold nanoclusters (D-Pen-capped, L-Pen-capped, or rac-Pen-capped clusters) by polyacrylamide gel electrophoresis (PAGE). Each fractioned component has the mean diameter of 0.57, 1.18, or 1.75 nm that was determined by a solution-phase small-angle X-ray scattering. With a decrease in the mean cluster diameter, optical activity or anisotropy factors gradually increased. On the basis of the kinetic and the structural considerations, the origins of large optical activity of the gold nanocluster enantiomers are discussed.

Infrared and ultraviolet laser spectroscopy of jet-cooled substituted salicylic acids; substitution effects on the excited state intramolecular proton transfer in salicylic acid

Substitution effects on the excited state intramolecular proton transfer (ESIPT) in the salicylic acid (SA) frame were studied by electronic and infrared spectroscopy of jet-cooled 5-methoxylsalicylic acid (5-MeOSA), 5-methylsalicylic acid (5-MeSA), 5-fluorosalicylic acid (5-FSA), 6-fluorosalicylic acid (6-FSA), and methyl salicylate (MS). Infrared spectra were measured in the 3 µm region for both the electronic ground (S0) and first excited (S1) states. The electronic excitation/emission spectra of 5-MeSA and 6-FSA showed the typical spectral features of ESIPT, which have been found in the spectra of SA. On the other hand, 5-MeOSA and 5-FSA exhibit a mirror-image relation between their excitation and emission spectra, which has been regarded as a result of the suppression of ESIPT. Despite such a remarkable difference among the electronic spectra, IR spectroscopy shows that a drastic change of the phenolic OH stretching vibration does occur upon electronic excitation of all substituted SAs, that is, the phenolic OH band of all the SAs disappears from the 3 µm region, indicating a large elongation of the phenolic O–H bond (over 0.1 Å) in S1. This result means that the intramolecular hydrogen bond strength is remarkably enhanced by electronic excitation in all the substituted SAs. Substitution effects on ESIPT in dimers are also discussed.

Another FIR lattice structure

A new two multiplier FIR lattice structure is derived by using the digital two-pair concept, which produces two transfer functions Hi(z) and Hi′(z) having the complementary relationship Hi′(z)=z−iHi(–z−1), in contrast to the mirror image relationship, i.e. Hi′(z)=z−iHi(z−1) satisfied in the conventional FIR lattice structure. The new structure should be useful in crossover networks as well as in multirate signal processing. Copyright © 2005 John Wiley & Sons, Ltd.

The nature of the rapid relaxation of excited charge-transfer complexes.

Examples of contact radical-ion-pair (CRIP) formation from excited charge-transfer (CT) complexes are described. The reduced absorption and emission spectra of the CT complexes formed between hexamethylbenzene, pentamethylbenzene, and durene donors and 1,2,4,5-tetracyanobenzene (TCNB) in 1,2-dichloroethane (DCLE) exhibit a mirror image relationship, suggesting that each set of spectra describes transitions between the same two states. It was concluded that a CRIP is produced immediately upon excitation of the CT complex and that relaxation of the CRIP includes only minor geometry changes and changes in solvent polarization. In contrast to these results, the reduced absorption and emission spectra of the mesitylene (MES)/TCNB CT complex in DCLE are distinctly different and do not display a mirror image relationship. Time-resolved emission decay traces reveal the presence of an initial intermediate species that contributes approximately 10% of the total steady-state emission. The emission spectrum of this initial species mirrors the absorption spectrum of the MES/TCNB complex. In the MES/TCNB complex, excitation does not lead directly to the CRIP, and the relaxation of the excited complex must include an electronic component in addition to changes in geometry and solvation. The implications of these results on the applicability of golden-rule expressions of electron transfer are discussed.