Förster resonance energy transfer (FRET) microscopy is widely used to study protein interactions in living cells. Typically, spectral variants of the Green Fluorescent Protein (FPs) are incorporated into proteins expressed in cells, and FRET between donor and acceptor FPs is assayed. As appreciable FRET occurs only when donors and acceptors are within 10 nm of each other, the presence of FRET can be indicative of aggregation that may denote association of interacting species. By monitoring the excited-state (fluorescence) decay of the donor in the presence and absence of acceptors, dual-component decay analysis has been used to reveal the fraction of donors that are FRET positive (i.e., in aggregates)._However, control experiments using constructs containing both a donor and an acceptor FP on the same protein repeatedly indicate that a large fraction of these donors are FRET negative, thus rendering the interpretation of dual-component analysis for aggregates between separately donor-containing and acceptor-containing proteins problematic. Using Monte-Carlo simulations and analytical expressions, two possible sources for such anomalous behavior are explored: 1) conformational heterogeneity of the proteins, such that variations in the distance separating donor and acceptor FPs and/or their relative orientations persist on time-scales long in comparison with the excited-state lifetime, and 2) FP dark states.

We demonstrate that resonant excitation of CdMnTe self-assembled quantum dots creates an ensemble of spin-polarized magnetic polarons at B=0 T. The strong spatial confinement characteristic of quantum dots significantly increases the stability of magnetic polarons so that the optically induced spin alignment is observed for temperatures > 120 K. *Author to whom the correspondence should be addressed: electronic mail: seb@physics. Incorporation of magnetic ions into semiconductor QDs offers the possibility of studying the interaction between carriers and magnetic ions under strong spatial electronic confinement [8][9][10]. It has been shown that EMPs confined in magnetic QDs, show significant enhancement of their thermal stability [11]. In addition, the spin relaxation time in non-magnetic semiconductor QDs has been found to be considerably longer than in QWs, reaching several hundreds of picoseconds [12,13]. One might thus anticipate that it might be possible to polarize Mn spins within a DMS QD by a suitably polarized exciton. 2In this letter we demonstrate the observation of optically induced magnetization of the Mn spins embedded in CdMnTe QDs. We show that through the resonant excitation of spinpolarized excitons one can control the alignment of zero-dimensional EMPs in QDs and therefore the magnetization direction of large QD ensembles. Moreover, due to significant enhancement of the stability of spin-polarized EMPs in these zero-dimensional nanostructures this optically induced spin alignment is observed above 120 K.The samples containing magnetic CdMnTe QDs and non-magnetic CdTe QDs were grown by molecular beam epitaxy on (100) Spin-polarized excitons were created resonantly in the QDs by LO phonon-assisted absorption into the QD ground states by both σ + -and σ − -polarized light [14]. Continuous wave argon ion-pumped dye laser (Rhodamine 590) was used as a tunable excitation source. The sample was placed in a variable temperature (from 4 K to 120 K) continuous-flow helium cryostat. Polarization of both excitation and emission was controlled by Babinet-Soleil compensators and Glan-Thomson linear polarizers, which enables the measurement of the emission intensity in both circular polarizations as a function of the excitation polarization. The emission was dispersed by a triple monochromator and detected by a cooled CCD camera. 3In Fig. 1a we show resonantly excited photoluminescence (PL) spectra for non-magneticCdTe QDs measured at B=0 T. If one excites the inhomogeneously broadened QD ensemble resonantly, spectral lines are observed that are significantly sharper than the non-resonant spectrum (shown by the shaded region in Fig. 1a). These lines are related to LO phonon-assisted absorption in QDs [14]. It is important to note that spin-polarized excitons are excited directly into the ground states of QDs responsible for this enhanced emission. For the resonant spectra shown in Fig. 1a the excitation is σ + -polarized while we analyze both σ + (circles) and σ − (squares) -polarized emission. We find that ...

Biodegradation-promoting additives for polymers are increasingly being used around the world with the claim that they effectively render commercial polymers biodegradable. However, there is a lot of uncertainty about their effectiveness in degrading polymers in different environments. In this study, we evaluated the effect of biodegradation-promoting additives on the biodegradation of polyethylene (PE) and polyethylene terephthalate (PET). Biodegradation was evaluated in compost, anaerobic digestion, and soil burial environments. None of the five different additives tested significantly increased biodegradation in any of these environments. Thus, no evidence was found that these additives promote and/or enhance biodegradation of PE or PET polymers. So, anaerobic and aerobic biodegradation are not recommended as feasible disposal routes for nonbiodegradable plastics containing any of the five tested biodegradation-promoting additives.

The rechargeable aqueous zinc–iodine (Zn–I2) battery has emerged as a promising electrochemical energy storage technology. However, poor cycling stability caused by the dissolution of iodine species into the electrolyte limited its practical application. Herein, we report a nitrogen-doped porous carbon (NPC) material in gram scales. Performed as an iodine host in the Zn–I2 battery, the NPC shows a high specific capacity (345.3 mAh g–1 at 0.2 C), superior rate capability (53.2% capacity retention at 10 C), and remarkable cycling stability (10 000 cycles at 10 C with a capacity retention of 80.9%). More importantly, DFT computations reveal that the graphitic-N (N-Q) exhibits the strongest adsorption of iodine; however, pyridinic-N (N-6) shows the weakest adsorption of iodine. Moreover, the N-6/N-Q ratio is an essential parameter that significantly determined the electrochemical performance of Zn–I2 batteries. Therefore, the improved long-term cycling stability and rate capability of the as-designed Zn–I2 battery are attributable to the decrease of the N-6/N-Q ratio. This work is of great significance for devolving highly reversible Zn–I2 batteries.

Förster resonance energy transfer (FRET) microscopy is frequently used to study protein interactions and conformational changes in living cells. The utility of FRET is limited by false positive and negative signals. To overcome these limitations we have developed Fluorescence Polarization and Fluctuation Analysis (FPFA), a hybrid single-molecule based method combining time-resolved fluorescence anisotropy (homo-FRET) and fluorescence correlation spectroscopy. Using FPFA, homo-FRET (a 1–10 nm proximity gauge), brightness (a measure of the number of fluorescent subunits in a complex), and correlation time (an attribute sensitive to the mass and shape of a protein complex) can be simultaneously measured. These measurements together rigorously constrain the interpretation of FRET signals. Venus based control-constructs were used to validate FPFA. The utility of FPFA was demonstrated by measuring in living cells the number of subunits in the α-isoform of Venus-tagged calcium-calmodulin dependent protein kinase-II (CaMKIIα) holoenzyme. Brightness analysis revealed that the holoenzyme has, on average, 11.9±1.2 subunit, but values ranged from 10–14 in individual cells. Homo-FRET analysis simultaneously detected that catalytic domains were arranged as dimers in the dodecameric holoenzyme, and this paired organization was confirmed by quantitative hetero-FRET analysis. In freshly prepared cell homogenates FPFA detected only 10.2±1.3 subunits in the holoenzyme with values ranging from 9–12. Despite the reduction in subunit number, catalytic domains were still arranged as pairs in homogenates. Thus, FPFA suggests that while the absolute number of subunits in an auto-inhibited holoenzyme might vary from cell to cell, the organization of catalytic domains into pairs is preserved.

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Incorporation of nanofillers into the organic coatings might enhance their barrier performance, by decreasing the porosity and zigzagging the diffusion path for deleterious species. Thus, the coatings containing nanofillers are expected to have significant barrier properties for corrosion protection and reduce the trend for the coating to blister or delaminate. On the other hand, high hardness could be obtained for metallic coatings by producing the hard nanocrystalline phases within a metallic matrix. This article presents a review on recent development of nanocomposite coatings, providing an overview of nanocomposite coatings in various aspects dealing with the classification, preparative method, the nanocomposite coating properties, and characterization methods. It covers potential applications in areas such as the anticorrosion, antiwear, superhydrophobic area, self-cleaning, antifouling/antibacterial area, and electronics. Finally, conclusion and future trends will be also reported.

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