A series of reduced-charge (RC) hectorites were prepared by multiple heat (250°C) treatments of Mg-saturated hectorites (SHCa-1 ). Cation exchange capacity (CEC) measurements and alkylammonium exchange indicated that a decrease in layer charge occurred with each Mg-250 treatment. Chemical analyses showed that decreases in structural Li and increases in structural Mg contents coincided with charge reduction. Fluorescence measurements of adsorbed quinoline indicated that the hectorite surface was acidified during charge reduction; hydroxyl group deprotonation is a possible source for the acidity. Fourier transform infrared spectra (FTIR) indicated that the Mg-250 treatment induced the loss of structural Li and shifted the SiO stretch band to a position similar to that in talc. The relative intensities of the OH and SiO stretch bands in FTIR spectra suggest that some of the hydroxyl groups in hectorite were lost, possibly by deprotonation. However, thermogravimetric data (TG) reveal no significant difference in the hydroxyl contents of the hectorites.

The FTIR spectra, CEC, layer charge, chemical, and TG data all supported the view that Mg substitution for octahedral Li occurred which resulted in a more “talc-like” structure. Charge reduction in smectites is evidently a general phenomenon and can be induced by heat treatment with the proper exchangeable cation. The ability to reduce the charge of hectorites makes it possible to prepare a series of clays which vary in charge but lack structural Fe. Such RC smectites should be suitable for expandable clay mineral studies which utilize spectroscopic techniques that are sensitive to Fe content.

Single Molecule Förster Resonance Energy Transfer (smFRET) is a popular technique to directly observe biomolecular dynamics in real time, offering unique mechanistic insight into proteins, ribozymes, and so forth. However, inevitable photobleaching of the fluorophores puts a stringent limit on the total time a surface-tethered molecule can be monitored, fundamentally limiting the information gain through conventional smFRET measurements. DyeCycling addresses this problem by using reversibly – instead of covalently – coupled FRET fluorophores, through which it can break the photobleaching limit and theoretically provide unlimited observation time. In this perspective paper, we discuss the potential of various fluorogenic strategies to suppress the background fluorescence caused by unbound, freely diffusing fluorophores inherent to the DyeCycling approach. In comparison to nanophotonic background suppression using zero-mode waveguides, the fluorogenic approach would enable DyeCycling experiments on regular glass slides with fluorogenic FRET probes that are quenched in solution and only fluoresce upon target binding. We review a number of fluorogenic approaches and conclude, among other things, that short-range quenching appears promising for realising fluorogenic DyeCycling on regular glass slides. We anticipate that our discussion will be relevant for all single-molecule fluorescence techniques that use reversible fluorophore binding.

Functions of mucin, as the major macromolecular component in saliva or gastric fluids, are drawing increasing attention in the context of understanding the oral processing or digestion of dairy foods at the molecular level. This study was designed to investigate the interactions between β-lactoglobulin (BLG)-lactose, mucin-lactose and BLG-lactose-mucin at the molecular level under different temperature and pH conditions using fluorescence spectroscopy in combination with scanning electron microscopes (sem). It is the first study of its kind. There was no lactose-dependent quenching on BLG fluorophore in the range of 0–10 mM lactose concentration. On the contrary, there was a continuous increase in the fluorescence intensity of the BLG protein when the lactose concentration increased, especially at 25°C. BLG-lactose complex became thermally unstable at 37 and 45°C. Moreover, BLG exhibited a pH dependent conformational change and had higher fluorescence intensity at pH 3 than pH 6.8. The fluorescence result was in correspondence with sem images where we observed lactose crystals gathering around and on the BLG molecule, but lactose molecules could not be seen in the presence of mucin. It was anticipated that mucin molecules interacted with BLG-lactose complex via electrostatic attraction and formed an extra protective layer around the BLG molecules to avoid solvent exposure.

Biophysical studies have a very high impact on the understanding of internalization, molecular mechanisms, interactions, and localization of CPPs and CPP/cargo conjugates in live cells or in vivo. Biophysical studies are often first carried out in test-tube set-ups or in vitro, leading to the complicated in vivo systems. This review describes recent studies of CPP internalization, mechanisms, and localization. The multiple methods in these studies reveal different novel and important aspects and define the rules for CPP mechanisms, hopefully leading to their improved applicability to novel and safe therapies.

Studies on the effect of nanofertilizers (NF) in physiological performance of plants is scarce, especially that related to substances encapsulated into silicon dioxide (SiO2) nanoparticles in cocoa plants. The effect of foliar application of SiO2-NF on nutrient contents, gas exchange, photochemical activity, photosynthetic pigments, total soluble protein (TSP), photosynthetic nitrogen use efficiency (PNUE), and growth in seedlings of two cocoa clones (OC-61 and BR-05) in a greenhouse was assessed. Spraying with SiO2-NF increased net photosynthetic rate (A) by 16 and 60% and electron transport rate (J) by 52 and 162% in clones OC-61 and BR-05, respectively, without changes in photosynthetic pigment concentration in either clone. The SiO2-NF caused a decrease of 37 and 22% in stomatal conductance in OC-61 and BR-05, respectively; a similar trend was observed in transpiration rate, causing an increase of 42 and 100% in water use efficiency in OC-61 and BR-05, respectively. In both clones, diameter of graft increased on average 28% with SiO2-NF. Higher photosynthetic capacity was related to an increase in leaf N, P, and TSP. A significant reduction in PNUE (A/N ratio) was found in OC-61, whereas in BR-05 PNUE increased after spraying with SiO2-NF. Overall, spraying with SiO2-NF had a positive effect on photosynthetic processes in both cocoa clones, associated with an increase in nutrients content, which translated into improved growth. A differential physiological response to spraying with SiO2-NF between clones was also found, with BR-05 being the clone with a better physiological response during the establishment and development stages.

Fluorescence in vivo endomicroscopy (FIVE) is a state-of-the-art endoscopy technique used to image tissue interactions and molecular events in a cell. In Part 1 of this series, the history, types of confocal laser endomicroscopy (CLE), and limitations of the technology were discussed. In Part 2 of the series, we describe several applications of FIVE technology, including advances in cancer, gastrointestinal, liver, rectal mucosal barrier function, acute lung injury, and brain imaging. Future perspectives for the technology are also presented.

We report infrared reflectance and ultraviolet fluorescence spectra of the surfaces and cleaved side of Beacon Sandstone from Antarctica that harbours a cryptoendolithic microbial community - a photosynthesis-based consortium of algae, lichen and bacteria present a few millimetres below the surface. Chlorophyll absorptions were present in the reflectance spectra of the exposed interior but not on the top or bottom surfaces and their band depths changed < 4% between measurements taken 19 years apart, indicating the stability of the microorganisms when the sample is kept dry. The presence of subsurface organic layers was detected in reflectance at 3.41 μm on the sample's surface. Fluorescence spectra of the cleaved side showed the blue fluorescence peaks expected from chlorophyll but no 0.65–0.80 μm peaks seen in fluorescence measurements of green vegetation. A weak fluorescence signal was detectable at the surface of the sample, presumably due to some light leaking into the subsurface through pores or cracks in the goethite coating the sample's surface. Theoretically, this weak fluorescence signal could possibly be observed in rock surfaces broken by erosion or meteor impacts on Mars. Sandstone outcrops have been reported on Mars and detection of organic layers in sandstones there would be of interest.

Accurate radiocarbon (14C) dating of lime mortars requires a thorough mineralogical characterization of binders in order to verify the presence of carbon-bearing contaminants. In the last 20 years, cathodoluminescence (CL) has been widely used for the identification of geologic calcium carbonate (CaCO3) aggregates and unreacted lime lumps within the particle size fraction selected for carbon recovery. These components are major sources of older and younger carbon, respectively, and should be removed to obtain accurate age determinations. More recently, laser-induced fluorescence (LIF) has provided another means of investigating the preservation state and composition of CaCO3 binders. Considered the growing interest of the mortar dating community in the latest advancements of these analytical methods, here we review the principles of CL and LIF of CaCO3, their instrument setup, and their application to the characterization of ancient lime mortars used for 14C dating. In addition, we provide examples of SEM-CL and LIF analyses using high-resolution instrumentation, we discuss current issues and propose future lines of research.

A simple composition of TeO2–Yb2O3 binary glass was selected as the host glass matrix for discussing the structure of tellurite glass with increasing Yb2O3 content. Raman spectra were measured to investigate the structure of the binary tellurite glasses, and upconversion and downconversion fluorescence characteristics were employed for discussing the relationship between the structural units and the state of Yb3+ in the tellurite glasses. The results suggested that the decrease of TeO4/2 in the glasses would result in the formation of Yb3+ clusters and Yb3+–O2− couple in the tellurite glasses, and then results in the decrease of cooperative upconversion and downconversion fluorescence intensity.

Despite its vital role in advancing live cell imaging (LCI) and unraveling the complex processes that control cellular function, fluorescence microscopy presents challenges for the researcher, including labeling agents that can interfere with normal molecular activities, and limitations on repeat measurements and long-term studies from photobleaching and phototoxicity phenomena. Holotomography microscopy delivers nanoscale, label-free, real-time LCI and can combine this quantitative phase imaging (QPI) with fluorescence for state-of-the-art spatiotemporal resolution as well as high molecular specificity. This article introduces QPI, examines its advantages for LCI, and reviews correlative microscopy studies in cell pathophysiology in combination with fluorescence.

LED illumination systems for fluorescence microscopy offer a wealth of benefits in comparison to traditional mercury and metal halide lamps, including ease of use, improved stability, and enhanced control. To fully realize these benefits, it is important to ensure that optical filters are configured correctly, which often can be confusing. However, without the correct filter configuration, experimental conditions can be suboptimal, and results may therefore be inaccurate. This article looks at optical filter setup in more depth, explaining the purpose and benefits of optimal LED filtering.

Replacing a portion of a glucose challenge with whole eggs (EGG) or egg whites (WHITE) was shown to protect against glucose-induced impairments in vascular function. We hypothesised in the present study that previously observed vasoprotection following co-ingestion of EGG or WHITE with glucose was attributed to limiting postprandial hyperglycaemia-induced oxidative stress that improves NO∙ bioavailability. Prediabetic men completed a randomised, cross-over study in which they ingested isoenergetic meals containing 100 g glucose (GLU), or 75 g glucose with 1·5 EGG, seven WHITE or two egg yolks (YOLK). At 30 min intervals for 3 h, we assessed plasma NO∙ metabolites, the lipid peroxidation biomarker malondialdehyde, antioxidants, arginine and its methylated metabolites (asymmetric dimethylarginine and symmetric dimethylarginine), tetrahydrobiopterin redox status, vasoconstrictors and inflammatory markers. Compared with GLU, malondialdehyde was lower and NO∙ metabolites were greater in EGG and WHITE, but YOLK was not different from GLU. Malondialdehyde was inversely correlated with NO∙ metabolites and vascular function, whereas NO∙ metabolites were positively correlated with vascular function. Compared with GLU, arginine was greater, but asymmetric and symmetric dimethylarginine and angiotensin-II were lower in all egg-based meals. Antioxidants, tetrahydrobiopterin redox status and inflammatory markers did not differ among treatments. Thus, while each egg-based meal improved arginine metabolism, only EGG and WHITE limited lipid peroxidation. This suggests that vasoprotection mediated by EGG and WHITE likely occurs in an NO∙-dependent manner by improving arginine metabolism and attenuating oxidative stress that otherwise limit NO∙ biosynthesis and bioavailability to the vascular endothelium.

In this paper, Sm3+-doped silicate glasses containing AgNO3 were obtained by the common melting quenching method. Influence of AgNO3 concentration on the absorption and emission characteristics of Sm3+ were systematically investigated. With the increase of AgNO3 content from 0 to 3.0 wt%, the ultraviolet region absorption edge shows a slight blue-shift from 275 to 260 nm. Exciting by 255 nm, the visible emission intensity of Sm3+-doped silicate glass containing 0.5 wt% AgNO3 was about 31 times stronger than that of Sm3+ singly doped silicate glass. Fluorescence decay curves for the visible emission followed double exponential decay. Two fluorescence lifetimes were obtained, one was about 7–20 μs which was comparable with the lifetimes of 350 nm emission which derived from Ag+, another was about 2 ms which was comparable with that of the visible emission from Sm3+ excited by 401 nm. Thus, the significant enhancement visible emission of Sm3+ excited by 255 nm can be ascribed to the energy transfer from Ag+ to Sm3+.

Fluorescence and phase transitions of a new Mg-Al-Eu ternary layered double hydroxide (LDH) and their dependence on thermal treatment were studied for the first time. Phase transitions occurred as the temperature increased from 400 to 1100°C. The process of phase transition is discussed in detail. The emissions of Eu3+ ions described by the 5D0–7FJ transition (J = 1,2,3,4), and especially for the 5D0–7FJ transition (J = 1,2) varied markedly with phase transformations from LDH, MgO, to mixtures of MgO and MgAl2O4. Moreover,strong emissions of Eu3+ ions are present in these new host materials. These results indicate that Mg-Al-Eu ternary LDH may be a potential candidate for materials applied in fluorescent devices.

The aggregation of three cationic dyes (CD), crystal violet (CV), Nile blue (NB) and rhodamine B (RB) in aqueous solution was studied by visible absorption spectrophotometry and compared with methylene blue (MB). The distribution of the dye species (monomers, dimers, trimers, and tetramers) in aqueous solutions with different concentrations of dye was calculated using equilibrium stepwise aggregation constants Kn. These cationic dyes were intercalated into montmorillonite (SAz-1) and its reduced charge form (RC-SAz(210)) prepared by heating lithium montmorillonite (Li/SAz-1) at 210ºC. The fluorescence of fully saturated CD/SAz and low-CD loaded CD/RC-SAz(210) complexes was studied. Visible absorption spectra of CD aqueous solutions and visible absorption spectra and X-ray diffraction patterns (d001) of the CD/SAz and CD/RC-SAz( 210) solid complexes were obtained and evaluated. Large fluorescence intensities were found for CV/RC-SAz(210) and NB/RC-SAz(210) complexes in the same way as for the complex of methylene blue with reduced-charge montmorillonite MB/RCM(210) described previously.

The activity of glyphosate [N-(phosphonomethyl)glycine], formulated as the isopropylamine salt, on in vitro photosynthesis was investigated. When pH 4.7 glyphosate solutions were titrated to a pH equal to that of the reaction media (pH 7.8), glyphosate additions had no effect on whole chain electron transport between coupled photosystem II (PS II) and photosystem I (PS I) in stroma-free chloroplast thylakoids from peas (Pisum sativum L. ‘Morse's Progress No. 9′). Inhibition did not occur even after a 2-h dark incubation of lamellae in a 5-mM solution of glyphosate. Fluorescence studies failed to detect an effect of glyphosate on PS-II mediated electron transport processes or upon light harvesting properties of PS II even after a 2-h glyphosate/chloroplast preincubation. Glyphosate had no effect on cyclic and noncyclic photophosphorylation even after a 100-min dark incubation of chloroplast membranes in a 5-mM solution of glyphosate. Based on these assays it is concluded that glyphosate has no direct effect on the photochemical reactions of photosynthesis when the pH of the active compound is adjusted to that of the reaction mixture prior to addition to a chloroplast suspension.

Partially purified glutathione-s-transferase (GST) isolated from corn (Zea mays L.) seedlings was about 14-fold higher in specific activity than GST isolated from giant foxtail (Setaria faberi Herrm. # SETFA) seedlings. Greater amounts of GST activity were present in leaf tissue than in stem tissue. Four-leaf giant foxtail seedlings contained about threefold more reduced glutathione per gram fresh weight in the leaves than one- to two-leaf giant foxtail seedlings. When atrazine and reduced glutathione were used as substrates, tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane] inhibited isolated GST from corn with an I50 of about 5 μM and from giant foxtail with an I50 slightly lower. Tridiphane inhibited the metabolism of atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] to water-soluble metabolites in giant foxtail leaves but not in corn leaves. Unmetabolized atrazine levels tended to be greater in giant foxtail seedlings treated with tridiphane plus atrazine than in plants treated with atrazine alone. Tridiphane applied 12 h before atrazine increased the uptake of atrazine in both corn and five-leaf giant foxtail seedlings. The amount of atrazine metabolism to water-soluble metabolites increased in corn leaves but remained constant in giant foxtail leaves when atrazine uptake was increased. Tridiphane and atrazine combinations impaired net photosynthetic rates more than atrazine alone in giant foxtail seedlings but did not increase chlorophyll fluorescence. There was no decrease in net photosynthetic rate 12 h following applications of atrazine or tridiphane plus atrazine on corn leaves. Tridiphane did not decrease photosynthesis or increase chlorophyll fluorescence in either species when applied alone.