Hydrophilic carotenoids: surface properties and aqueous aggregation of a rigid, long-chain, highly unsaturated dianionic bolaamphiphile with a carotenoid spacer

The water dispersibility of astaxanthin was greatly enhanced by converting it to a disodium disuccinate salt. This carotenoid salt behaved as a bolaamphiphile in water; dynamic light scattering (DLS) revealed the formation of stable aggregates with an average hydrodynamic radius close to 1 microm. Larger aggregates were observed in solutions of increased osmolarity. Absorption spectra demonstrated that the aggregates could withstand the addition of 20% acetonitrile before disintegrating to monomers. The physicochemical properties of this astaxanthin derivative in solution were comprehensively studied by measuring surface tension, critical aggregate concentration, surface concentration, molecule area, free energy of adsorption and micellation, adsorption-aggregate energy relationship, and equilibrium constants, and then compared with similar compounds reported previously in the literature.     

Hydrophilic carotenoids: surface properties and aggregation of an astaxanthin-lysine conjugate, a rigid, long-chain, highly unsaturated and highly water-soluble tetracationic bolaamphiphile

The surface and aggregation properties of a synthetic, highly water-soluble carotenoid, the tetracationic astaxanthin-lysine conjugate (Asly), have been examined through measurements of surface tension, optical absorption and dynamic light scattering. The following parameters were determined: critical aggregation concentration c(M), surface concentration Gamma, molecular area a(m), free energy of adsorption and aggregation (DeltaG(ad) degrees and DeltaG(M) degrees , respectively), and the aggregate size r(H). The compound forms true monomolecular solutions in water below c(M); aggregates emerge only at rather high concentrations (> or =2.18 mM).     

Non-covalent associations of cyclomaltooligosaccharides (cyclodextrins) with carotenoids in water. A study on the alpha- and beta-cyclodextrin/psi,psi-carotene (lycopene) systems by light scattering,ionspray ionization and tandem mass spectrometry

Water-soluble complexes of the dietary carotenoid psi,psi-carotene (lycopene 1) with cyclomaltohexaose (alpha-cyclodextrin, alphaCD) and cyclomaltoheptaose (beta-cyclodextrin, betaCD) have been prepared and characterized via multiangle light scattering (MALS), ionspray/electrospray ionization (IS/ESI) mass spectrometry (MS) and tandem MS. MALS experiments point out that large aggregates of particles, on the nanometer-size scale, are present in water, with meaningful differences in the shape of the alphaCD/1 aggregates with respect to betaCD/1 analogues. The true 1:1 alphaCD/1 inclusion complex has been observed by IS/ESIMS and confirmed by tandem MS. The structure of CD/1 aggregations in water is proposed which are consistent with the combined MALS and MS experimental results.     

Hydrophilic carotenoids: facile syntheses of carotenoid oxime hydrochlorides as long-chain, highly unsaturated cationic (bola)amphiphiles

Stable cationic carotenoid aggregates — predominantly of the J-type — develop when the hydrochlorides of carotenoid aldoximes and ketoximes are exposed to water. The oxime hydrochlorides are obtained by simple syntheses from commercially available food color carotenoids. Bluish-purple, unstable transient compounds were observed during hydrochlorination performed at liquid nitrogen temperature.     

Singlet oxygen quenching by dietary carotenoids in a model membrane environment

The ability of several dietary carotenoids to quench singlet oxygen in a model membrane system (unilamellar DPPC liposomes) has been investigated. Singlet oxygen was generated in both the aqueous and the lipid phase, with quenching by a particular carotenoid independent of the site of generation. However, singlet oxygen quenching is dependent on the carotenoid incorporated; xanthophylls exhibit a marked reduction in efficiency compared to the hydrocarbon carotenoids. Lycopene and beta-carotene exhibit the fastest singlet oxygen quenching rate constants (2.3-2.5 x 10(9)M(-1)s(-1)) with lutein the least efficient (1.1 x 10(8)M(-1)s(-1)). The other carotenoids, astaxanthin and canthaxanthin, are intermediate. Zeaxanthin exhibits anomalous behavior, and singlet oxygen quenching decreases with increasing amounts of zeaxanthin, leading to nonlinear plots for the decay of singlet oxygen with zeaxanthin concentration. Such differences are discussed in terms of carotenoid structure and their influence on the properties of the lipid membrane. The formation of aggregates by the polar carotenoids is also proposed to be of significance in their ability to quench singlet oxygen.     

Polymer-mediated electrostatic interactions between charged lipid assemblies and electrolyte solutions: a tentative model of the polyethylene glycol-induced cell fusion

We developed a theoretical model to investigate the interaction between charged lipid aggregates and a water solution containing ions and uncharged polymers. The local concentration of ions and polymer chains around the lipid aggregate have been treated as variational parameters which can be found by minimizing the total energy of the system. We divided the energy into the following main contributions: (a) Solvation energy of the ions. This depends on the local polymer concentration through the variation of the solvent dielectric properties. (b) Ions-lipid aggregate interactions. These depend on the local concentrations both of the ion cloud and polymer chains. (c) Conformational energy of the polymer. This term is related to the inhomogeneous spatial density of the polymer segments. Any direct interaction between the charged lipid surface and the polymer coils has been intentionally neglected. The minimization procedure leads to a non-linear Poisson-Boltzmann equation coupled with a non-linear algebraic equation describing the polymer distribution. The solution of the above system allows one to calculate the ions and polymer spatial distribution around the lipid aggregate. The knowledge of such parameters is useful to predict the effect of non-ionic polymers on the structure and properties of lipid assemblies such as the mean area per lipid molecule, the aggregation number, the critical micellar concentration and the formation of immiscibility gaps in mixed lipid systems. A possible involvement of these parameters into the fusion process between lipid vesicles is discussed.     

Oligomerization of hydrophobin SC3 in solution: from soluble state to self-assembly

Hydrophobin SC3 is a protein with special self-association properties that differ depending on whether it is in solution, on an air/water interface or on a solid surface. Its self-association on an air/water interface and solid surface have been extensively characterized. The current study focuses on its self-association in water because this is the starting point for the other two association processes. Size-exclusion chromatography was used to fractionate soluble-state SC3. Real-time multiangular light scattering detection of the eluate indicated that SC3 mainly exists as a dimer in buffer, accompanied with a small amount of monomer, tetramer, and larger aggregates. Dimeric SC3 has very likely an elongated shape, as indicated by the hydrodynamic radius determined by using dynamic light scattering (DLS) and fluorescence anisotropy measurements on dansyl-labeled SC3. Size-exclusion chromatography experiments also indicated that the protein oligomerizes very slowly at low temperature (4 degrees C) but rather rapidly at room temperature. Ionic strength plays an important role in the oligomerization; a short-lived monomeric SC3 species could be observed in pure water. Oligomerization was not affected by low pH but was accelerated by high pH. Fluorescence resonance energy transfer showed that dissociation occurred when the protein concentration was lowered; a large population of oligomers, presumably dimers, dissociate when the protein concentration is <4.5 microg/mL. This value is similar to the critical concentration for SC3 self-assembly. Therefore, dimeric SC3 is indicated to be the building block for both aggregation in solution and self-assembly at hydrophobic/hydrophilic interfaces.     

Fluorescence life-times and aggregation states of the core light harvesting complex B875 from Rubrivivax gelatinosus

The core light-harvesting complex B875 isolated from the purple bacterium Rubrivivax gelatinosus and its different spectral forms B820 and B840, which are depleted of carotenoid, were investigated by steady-state and time-resolved fluorescence, and by electron microscopy. Images of B875 have been shown to contain cyclic oligomers with a diameter of 150–200 Å and with a central hole of 25 Å [Jirsakova V, Reiss-Husson F and Ranck JL (1996) Biochim Biophys Acta 1277: 150–160]. Dilute B820 samples contained heterogeneous, compact particles that tend to aggregate with increasing concentration of protein, forming clumps without any visible substructure. At the same time the absorption maximum of such aggregates shifted to 840 nm. Fluorescence emission and life times were analyzed by single photon counting. In B875 samples the major component emitted at 892 nm with a life time of 0.64 ns. B820 samples emitted at 830 nm with a life-time of 1 ns. An additional short life-time component of 0.3–0.4 ns was found in B820 and emitted at about 860 nm; its contribution increased with the B820 concentration. This latter component is attributed to the fluorescence quenching occuring within the non-native aggregates of B820 formed in the absence of carotenoid. When the B875 antenna was reconstituted from B820 subunit and hydroxyspheroidene, it presented an emission spectrum and a fluorescence decay identical to those observed in the native core complex, pointing to the structural role of the carotenoid for the proper architecture of this antenna.     

Self-organized Polymer Aggregates with a Biomimetic Hierarchical Structure and its Superhydrophobic Effect

Nature always gives us inspirations to fabricate functional materials by mimicking the structure design of biomaterials. In this article, we report that polymeric aggregates with morphology similar to the papilla on lotus leaf can be self-organized in the polymer solution by adding 16 wt% water into 5 mg/ml polycarbonate solution in N, N′-dimethylformamide. The hierarchically structured aggregates at micro- and nano-scale alone show superhydrophobic effect without the need of modification with low surface energy compound. Small amount of liquid can be wrapped by the aggregates to form the so-called liquid marble. Influence of the amount of water added into the solution on the morphology of resultant polymer aggregates was investigated. By using the hierarchical aggregates as the surface building blocks, superhydrophobic coating with a static water contact angle larger than 160° and sliding angle less than 5° (for a water drop of 5 μl) was formed. Other solutions, like acid, basic and blood plasma are also repelled on the coating.     

Quenching of fluorescence by triplet excited states in chloroplasts

The fluorescence quantum yield in spinach chloroplasts at room temperature has been studied utilizing a 0.5-4.0 mus duration dye laser flash of varying intensities as an excitation source. The yield (phi) and carotenoid triplet concentration were monitored both during and following the laser flash. The triplet concentration was monitored by transient absorption spectoscopy at 515 nm, while the yield phi following the laser was probed with a low intensity xenon flash. The fluorescence is quenched by factors of up to 10-12, depending on the intensity of the flash and the time interval following the onset of the flash. This quenching is attributed to a quencher Q whose concentration is denoted by Q. The relative instantaneous concentration of Q was calculated from phi utilizing the Stern-Volmer equation, and its buildup and decay kinetics were compared to those of carotenoid triplets. At high flash intensities (greater than 10(16) photon . cm-2) the decay kinetics of Q are slower than those of the carotenoid triplets, while at lower flash intensities they are similar. Q is sensitive to oxygen and it is proposed that Q, at the higher intensities, is a trapped chlorophyll triplet. This hypothesis accounts well for the continuing rise of the carotenoid triplet concentration for 1-2 mus after the cessation of the laser pulse by a slow detrapping mechanism, and the subsequent capture of the triplet energy by carotenoid molecules. At the maximum laser intensities, the carotenoid triplet concentration is about one per 100 chlorophyll molecules. The maximum chlorophyll ion concentration generated by the laser pulses was estimated to be below 0.8 ions/100 chlorophyll molecules. None of the observations described here were altered when a picosecond pulse laser train was substituted for the microsecond pulse. A simple kinetic model describing the generation of singlets and triplets (by intersystem crossing), and their subsequent interaction leading to fluorescence quenching, accounts well for the observations. The two coupled differential equations describing the time dependent evolution of singlet and triplet excited states are solved numerically. Using a single-triplet bimolecular rate constant of gammast = 10(-8) cm3 . s-1, the following observations can be accounted for: (1) the rapid initial drop in phi and its subsequent levelling off with increasing time during the laser pulse, (2) the buildup of the triplets during the pulse, and (3) the integrated yield of triplets per pulse as a function of the energy of the flash.     

Raman spectroscopic analysis of the carotenoid concentration in egg yolks depending on the feeding and housing conditions of the laying hens

Resonance Raman spectroscopic measurements are suited to analyze the concentration of carotenoid antioxidants in biological samples. Previously, it has been shown that the carotenoid concentration of nutritional egg yolks has a direct influence on the carotenoid content of human skin in vivo. In the present study, resonance Raman spectroscopy was used to analyze the carotenoid concentration in the yolks of hen eggs, which were housed in battery cages or alternatively on free‐range grassland. The egg yolks of hens, which had access to grassland, contained approximately double the amount of carotenoid concentration than the egg yolks of hens housed in battery cages (p < 0.001). The kinetics of the carotenoid concentration in the egg yolks, depending on fodder, housing and weather conditions, were investigated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Origin and composition of settling iron aggregates in oligotrophic Sombre Lake, Signy Island, Antarctica

Sediment traps were deployed in an oligotrophic, seasonally anoxic maritime Antarctic lake for 15 months. Immediately after the onset of the inflow in spring many iron oxyhydroxide aggregates were collected in the traps. Image analysis, scanning electron microscopy and energy dispersive X-ray analysis were used to examine the aggregates.The aggregates consisted of primary particles that persisted in the aggregates. The mean diameter of the aggregates was constant with depth. The aggregates consisted predominantly of iron, phosphorus and oxygen but calcium was also an important constituent. Significant concentrations of manganese and sodium were also detected. The molar ratio Fe:P remained constant at 4:1 as did the ratio Fe:Ca at 52:1. The concentration of iron, phosphorus and calcium in the aggregates increased with depth, whilst the concentration of manganese decreased with depth in parallel with a gradient of increasing anoxia.The stable water column formed under ice cover and the temporal and spatial data provide evidence that the Fe:P and Fe:Ca ratios are constant and characteristic of the aggregates, whilst the overall composition of the aggregates is more dynamic and dependant on redox conditions and water chemistry.     

Quenching of fluorescence by triplet excited states in chloroplasts

The fluorescence quantum yield in spinach chloroplasts at room temperature has been studied utilizing a 0.5–4.0 μs duration dye laser flash of varying intensities as an excitation source. The yield (Ф) and carotenoid triplet concentration were monitored both during and following the laser flash. The triplet concentration was monitored by transient absorption spectroscopy at 515 nm, while the yield Ф following the laser was probed with a low intensity xenon flash. The fluorescence is quenched by factors of up to 10–12, depending on the intensity of the flash and the time interval following the onset of the flash. This quenching is attributed to a quencher Q whose concentration is denoted by Q. The relative instantaneous concentration of Q was calculated from Ф utilizing the Stern-Volmer equation, and its buildup and decay kinetics were compared to those of carotenoid triplets. At high flash intensities (10¹⁶ photon · cm⁻²) the decay kinetics of Q are slower than those of the carotenoid triplets, while at lower flash intensities they are similar. Q is sensitive to oxygen and it is proposed that Q, at the higher intensities, is a trapped chlorophyll triplet. This hypothesis accounts well for the continuing rise of the carotenoid triplet concentration for 1–2 μs after the cessation of the laser pulse by a slow detrapping mechanism, and the subsequent capture of the triplet energy by carotenoid molecules.

At the maximum laser intensities, the carotenoid triplet concentration is about one per 100 chlorophyll molecules. The maximum chlorophyll ion concentration generated by the laser pulses was estimated to be below 0.8 ions/100 chlorophyll molecules. None of the observations described here were altered when a picosecond pulse laser train was substituted for the microsecond pulse.

A simple kinetic model describing the generation of singlets and triplets (by intersystem crossing), and their subsequent interaction leading to fluorescence quenching, accounts well for the observations. The two coupled differential equations describing the time dependent evolution of singlet and triplet excited states are solved numerically. Using a singlet-triplet bimolecular rate constant of γ_st = 10⁻⁸ cm³ · s⁻¹, the following observations can be accounted for: (1) the rapid initial drop in Ф and its subsequent levelling off with increasing time during the laser pulse, (2) the buildup of the triplets during the pulse, and (3) the integrated yield of triplets per pulse as a function of the energy of the flash.     

The Cyanobacterial Photoactive Orange Carotenoid Protein Is an Excellent Singlet Oxygen Quencher

Cyanobacteria have developed a photoprotective mechanism that decreases the energy arriving at the photosynthetic reaction centers under high-light conditions. The photoactive orange carotenoid protein (OCP) is essential in this mechanism as a light sensor and energy quencher. When OCP is photoactivated by strong blue-green light, it is able to dissipate excess energy as heat by interacting with phycobilisomes. As a consequence, charge separation and recombination leading to the formation of singlet oxygen diminishes. Here, we demonstrate that OCP has another essential role. We observed that OCP also protects Synechocystis cells from strong orange-red light, a condition in which OCP is not photoactivated. We first showed that this photoprotection is related to a decrease of singlet oxygen concentration due to OCP action. Then, we demonstrated that, in vitro, OCP is a very good singlet oxygen quencher. By contrast, another carotenoid protein having a high similarity with the N-terminal domain of OCP is not more efficient as a singlet oxygen quencher than a protein without carotenoid. Although OCP is a soluble protein, it is able to quench the singlet oxygen generated in the thylakoid membranes. Thus, OCP has dual and complementary photoprotective functions as an energy quencher and a singlet oxygen quencher.     

Pulse ENDOR and density functional theory on the peridinin triplet state involved in the photo-protective mechanism in the peridinin-chlorophyll a-protein from Amphidinium carterae

The photoexcited triplet state of the carotenoid peridinin in the Peridinin-chlorophyll a-protein of the dinoflagellate Amphidinium carterae has been investigated by pulse EPR and pulse ENDOR spectroscopies at variable temperatures. This is the first time that the ENDOR spectra of a carotenoid triplet in a naturally occurring light-harvesting complex, populated by energy transfer from the chlorophyll a triplet state, have been reported. From the electron spin echo experiments we have obtained the information on the electron spin polarization dynamics and from Mims ENDOR experiments we have derived the triplet state hyperfine couplings of the alpha- and beta-protons of the peridinin conjugated chain. Assignments of beta-protons belonging to two different methyl groups, with aiso=7.0 MHz and aiso=10.6 MHz respectively, have been made by comparison with the values predicted from density functional theory. Calculations provide a complete picture of the triplet spin density on the peridinin molecule, showing that the triplet spins are delocalized over the whole pi-conjugated system with an alternate pattern, which is lost in the central region of the polyene chain. The ENDOR investigation strongly supports the hypothesis of localization of the triplet state on one peridinin in each subcluster of the PCP complex, as proposed in [Di Valentin et al. Biochim. Biophys. Acta 1777 (2008) 186-195]. High spin density has been found specifically at the carbon atom at position 12 (see Fig. 1B), which for the peridinin involved in the photo-protective mechanism is in close contact with the water ligand to the chlorophyll a pigment. We suggest that this ligated water molecule, placed at the interface between the chlorophyll-peridinin pair, is functioning as a bridge in the triplet-triplet energy transfer between the two pigments.     

子午岭次生林植被演替过程的土壤抗冲性

在水土流失极为严重的黄土高原地区,土壤抗冲性决定着土壤的可蚀性.于2004年5月在黄土高原惟一的次生林区——子午岭林区,通过原状土冲刷实验对不同植被演替阶段下的土壤抗冲性进行了研究.结果表明： （1）随植被的正向演替,表层土壤（0～15cm）的抗冲性明显增大,但亚表层（15～30cm）和底层（30～50cm）土壤抗冲性则没有太大的变化;（2）植物根系能显著的增强土壤抗冲性,土壤抗冲系数与单位土体根系表面积具有极显著的（p＜0.001）线性相关关系;（3）土壤抗冲系数随土壤中水稳性团聚体含量和微生物量的增加而增大,且其相关关系极显著（p＜0.001）.综合根系（x1）、水稳性团聚体（x2）以及微生物（x3）对土壤抗冲性的影响,建立黄土高原地区土壤抗冲性方程： y=-4.89＋1.27x1＋0.079x2＋1.94E-3x3 （R^2=0.914 p＜0.001）.     

Dietary carotenoids predict plumage coloration in wild house finches

Carotenoid pigments are a widespread source of ornamental coloration in vertebrates and expression of carotenoid-based colour displays has been shown to serve as an important criterion in female mate choice in birds and fishes. Unlike other integumentary pigments, carotenoids cannot be synthesized; they must be ingested. Carotenoid-based coloration is condition-dependent and has been shown to be affected by both parasites and nutritional condition. A controversial hypothesis is that the expression of carotenoid-based coloration in wild vertebrates is also affected by the amount and types of carotenoid pigments that are ingested. We tested this carotenoid-limitation hypothesis by sampling the gut contents of moulting house finches and comparing the concentration of carotenoid pigments in their gut contents with the colour of growing feathers. We found a positive association: males that ingested food with a higher concentration of carotenoid pigments grew brighter ornamental plumage. We also compared the concentration of carotenoids in the gut contents of males from two subspecies of house finches with small and large patches of carotenoid-based coloration. Consistent with the hypothesis that carotenoid access drives the evolution of carotenoid-based colour displays, males from the population with limited ornamentation had much lower concentrations of carotenoids in their gut contents than males from the population with extensive ornamentation. These observations support the idea that carotenoid intake plays a part in determining the plumage brightness of male house finches.     

Fluorescence study of the energetics of nucleotide-actinomycin complexes

Complexes of 7-aminoactinomycin D (7AAMD), a fluorescent analogue of the natural antitumor antibiotic actinomycin D (AMD), with its potential carriers: purine nucleotides (guanine and adenine), caffeine, and fragmented DNA have been studied by fluorescence spectroscopy. It has been shown that 7AAMD binds on the surface of purine aggregates and caffeine clusters and is particularly well incorporated into unwound DNA regions. The process is accompanied by a strong long-wavelength shift of the excitation spectrum of 7AAMD. From the magnitude of the shift, the energy of interaction has been found. In the case of the interaction of 7AAMD with guanine, adenine, and caffeine, it is about 7 kcal/mol, which differs little from the energy of its interaction with DNA (7.7 kcal/mol). This indicates that the contribution of deoxyribose and phosphate to the energy of interaction is very small. On interaction with all compounds examined, except DNA, 7AAMD emits from the water phase, as judged from emission spectra. It has been concluded that, upon photoexcitation, 7AAMD passes readily from all clusters to the polar water phase but does not leave DNA and remains in the hydrophobic surroundings. Presumably, the rigidity of the binding of 7AAMD is determined not only by the enthalpic energy of interaction but also the entropic steric factor, the location of the antibiotic in the hydrophobic part of the unwound region.     

Physiology of purple sulfur bacteria forming macroscopic aggregates in Great Sippewissett Salt Marsh, Massachusetts

Abstract Purple bacterial aggregates found in tidal pools of Great Sippewissett Salt Marsh (Falmouth, Cape Cod, MA) were investigated in order to elucidate the ecological significance of cell aggregation. Purple sulfur bacteria were the dominant microorganisms in the aggregates which also contained diatoms and a high number of small rod-shaped bacteria. Urea in concentrations of ≥ 1 M caused disintegration of the aggregates while proteolytic enzymes, surfactants or chaotropic agents did not exhibit this effect. This suggests that polysaccharides in the embedding slime matrix stabilize the aggregate structure. In addition cell surface hydrophobicity is involved in aggregate formation. The concentration of dissolved oxygen decreased rapidly below the surface of aggregates while sulfide was not detected. The apparent respiration rate in the aggregates was high when the purple sulfur bacteria contained intracellular sulfur globules. In the presence of DCMU, respiration remained light-inhibited. Light inhibition disappeared in the presence of KCN. These results demonstrated that respiration in the aggregates is due mainly to purple sulfur bacteria. The concentration of bacteriochlorophyll (Bchl) a in the aggregates (0.205 mg Bchl a cm⁻³) was much higher than in the pool sediments but comparable to concentrations in microbial mats of adjacent sand flats. Purple aggregates may therefore originate in the microbial mats rather than in the pools themselves. Rapid sedimentation and high respiration rates of Chromatiaceae in the aggregates would prevent the inhibition of Bchl synthesis if aggregates were lifted off the sediment and up into the oxic pool water by tidal currents.     

Surface Plasmon Tunability and Emission Sensitivity of Ultrasmall Fluorescent Copper Nanoclusters

Ultrasmall copper nanoparticles have been synthesized using copper(II) salt as precursor by hydrazine reduction in the presence of citric acid and cetyltrimethylammonium bromide facilitating the growth of stable copper nanoparticles with an average diameter of <2 nm. The corresponding surface plasmon resonances were monitored under variable microenvironments, and it is seen that these tiny copper nanoparticles form aggregates under stipulated reaction conditions. It is noted that ultrasmall copper nanoparticles do not exhibit any characteristic surface plasmon band in the visible region; rather, a continuous absorption is seen over the entire UV–vis region. However, a well-defined plasmon absorption band makes its appearance while the particles are aggregated in close-packed assembly. These results demonstrate that the maximum of surface plasmon resonance is red-shifted from that of isolated particles because of electromagnetic interaction between the particles. The aggregation process is manifested upon changes of pH, anionic surfactant, etc. and is not reversible, i.e., the aggregates could not be re-dispersed into ultrasmall particles. The effect of addition of electrolyte has been monitored to study the surface plasmon damping of the copper nanoparticles. The plasmonic sensitivity of the copper nanoparticle aggregates has been elicited by the determination of amino acid chain length with exquisite sensitivity because of enormous electromagnetic field at the junction of the particles in the aggregates. Interestingly, the as-synthesized ultrasmall copper nanoclusters exhibit excellent fluorescence properties with a narrow emission profile. The emission properties of these copper nanoclusters have been utilized as an indicator for selective and ultrasensitive detection of highly toxic Hg^II ions in water in the nanomolar detection limit.