Similar or Totally Different: the Adjustment of the Twist Conformation Through Minor Structural Modification,and Dramatically Improved Performance for Dye‐Sensitized Solar Cell

A novel approach for enhancing the performance of dye‐sensitized solar cells is presented. It is based on the analysis of five sensitizers by utilizing triarylamine as donor, thiophene benzothiadiazole as chromophore and substituted thienyl linked with cyanoacrylic acid as the anchoring group (LI‐80‐LI‐84). Accompanied with the increasing steric hindrance of the substituents on the thienyl isolation group, the conformation of the dyes, in particular the angle between the chromophore and the anchoring group, becomes more and more twisted. Surprisingly, sensitizers with poorer conjugation effects (the higher twisted conformation) achieve better photovoltaic performances, showing a contrary trend to the traditional donor‐(π‐spacer)‐acceptor dyes with a better co‐planarity. On the basis of the preceding fundamental comprehensions, an empirical method is successfully applied to a new phenyl‐based system (LI‐85 and LI‐86) to improve their performances. The systematical investigation indicates that the twisted structures can contribute to the E_CB of the TiO₂ film, electron lifetime and resistance at the TiO₂/dye/electrolyte interface. Thereby, the efficiency of the initial LI‐80‐based cell has been dramatically improved to 2.45 times higher for LI‐86‐based cell, paving a new way for the design of better sensitizers with higher device performances.     

Study on the interaction of a cyanine dye with human serum transferrin

Complexation between the primary carrier of ligands in blood plasma, human serum transferrin (Tf), and a cyanine dye, 3,3′‐di(3‐sulfopropyl)‐4,5,4′,5′‐dibenzo‐9‐phenyl‐thiacarbocyanine‐triethylam monium salt (PTC) was investigated using fluorescence spectra, UV/Vis absorption spectra, synchronous fluorescence spectra, circular dichroism (CD) and molecular dynamic docking. The experimental results demonstrate that the formation of PTC–Tf complex is stabilized by van der Waal's interactions and hydrogen bonds, and the binding constants were found to be 8.55 × 10⁶, 8.19 × 10⁶ and 1.75 × 10⁴ M^?1. Moreover, fluorescence experiments prove that the operational mechanism for the fluorescence quenching is static quenching and non‐radiative energy transfer. Structural investigation of the PTC–Tf complexes via synchronous fluorescence spectra and CD showed that the structure of Tf became more stable with a major increase in the α‐helix content and increased polarity around the tryptophan residues after PTC binding. In addition, molecular modeling highlights the residues located in the N‐lobe, which retain high affinity for PTC. The mode of action of the PTC–Tf complex is illustrated by these results, and may provide an effective pathway for the transport and targeted delivery of antitumor agents. Copyright © 2015 John Wiley & Sons, Ltd.     

A New Organic Dye-Based Staining for The Detection of Plant DNA in Agarose Gels

Ethidium bromide (EtBr) is used to stain DNA in agarose gel electrophoresis, but this dye is mutagenic and carcinogenic. We investigated N-719, which is a visible, reliable and organic Ruthenium-based dye, and five fluorescent alternatives for staining plant DNA. For prestaining and poststaining, N-719, GelRed, and SYBR Safe stained both DNA and PCR product bands as clearly as EtBr. SYBR Green I, methylene blue, and crystal violet were effective for poststaining only. The organic dye N-719 stained DNA bands as sensitively and as clearly as EtBr. Consequently, organic dyes can be used as alternatives to EtBr in plant biotechnology studies.     

Comparison of three common DNA concentration measurement methods

Accurate measurement of DNA concentration is important for DNA-based biological applications. DNA concentration is usually determined by the ultraviolet (UV) absorption, fluorescence staining, and diphenylamine reaction methods. However, the best method for quality assurance of measurements is unknown. Here, we comprehensively compared these methods using different types of samples. We found that all three methods accurately determined the concentrations of high-purity DNA solutions. After digestion of DNA samples, concentration measurements revealed that the PicoGreen dye method was very sensitive to the degradation of DNA. The three methods displayed different anti-jamming ability when contaminants such as transfer RNA (tRNA), protein, and organic chemicals were included in DNA solutions. The diphenylamine reaction method gave the highest accuracy, with an average error of approximately 10% between measured and true values. The PicoGreen dye method was influenced by tRNA and protein, and the UV absorption method was susceptible to all kinds of impurities. Overall, the diphenylamine reaction method gave the most accurate results when DNA was mixed with contaminants, the PicoGreen dye method was most suitable for degraded DNA samples or DNA extracted from processed products, and the UV absorbance method was best for evaluating the impurities in DNA solutions.     

Direct and simple detection of recombinant proteins from cell lysates using differential scanning fluorimetry

A simple, inexpensive, and universal method to quantify the recombinant proteins in Escherichia coli cell lysate using differential scanning fluorimetry (DSF) is reported. This method is based on the precise correlation between Δ(fluorescence intensity) determined by DSF and the amount of protein in solution. We first demonstrated the effectiveness of the DSF method using two commercially available enzymes, α-amylase and cellobiase, and then confirmed its utility with two recombinant proteins, amylosucrase and maltogenic amylase, expressed in E. coli. The Δ(fluorescence intensity) in DSF analysis accurately correlated with the concentration of the purified enzymes as well as the recombinant proteins in E. coli cell lysates. The main advantage of this method over other techniques such as Western blotting, enzyme-linked immunosorbent assay (ELISA), and green fluorescence protein (GFP) fusion proteins is that intact recombinant protein can be quantified without the requirement of additional chemicals or modifications of the recombinant protein. This DSF assay can be performed using widely available equipment such as a real-time polymerase chain reaction (RT–PCR) instrument, microplates or microtubes, and fluorescent dye. This simple but powerful method can be easily applied in a wide range of research areas that require quantification of expressed recombinant proteins.     

Studies on solvatochromic properties of aminophenylstyryl-quinolinum dye, LDS 798, and its application in studying submicron lipid based structure

The styryl group of dyes has been used in cellular studies for over 20 years because of their solvatochromic and/or electrochromic properties. Here we report characterization of solubility and solvatochromic properties of a near infra-red styryl dye, styryl 11 or LDS 798. We have extended our studies to small unilamellar vesicles and lipid based nanoparticles and found that solvatochromic properties of this dye used in tandem with fluorescence correlation spectroscopy can be used to efficiently determine the diffusion coefficient and hence the size of the submicron lipid based particles. This technique has the potential to provide essential information about liposomal and vesicular structures and their movement in vitro and in situ.     

Formation of amyloids by Abeta-(1-42) on NGF-differentiated PC12 cells: roles of gangliosides and cholesterol

The conversion of soluble, non-toxic amyloid beta-protein (Abeta) to aggregated, toxic Abeta could be the key step in the development of Alzheimer's disease. Liposomal studies have proposed that Abeta-(1-40) preferentially recognizes a cholesterol-dependent cluster of gangliosides and a conformationally altered form of Abeta promotes the aggregation of the protein. Cell experiments using fluorescein-labeled Abeta-(1-40) supported this model. Here, the interaction of native Abeta-(1-42) with unfixed rat pheochromocytoma PC12 cells was visualized using the amyloid-specific dye Congo red. Abeta-(1-42) preferentially bound to ganglioside and cholesterol-rich domains of cell membranes and formed amyloids in a time-dependent manner. These observations corroborate the model involving ganglioside-mediated accumulation of Abeta. The NGF-induced differentiation of PC12 cells into neuron-like cells caused a marked increase in both gangliosides and cholesterol, and thereby greatly potentiated the accumulation and cytotoxicity of Abeta-(1-42). NGF-differentiated cells exposed to Abeta-(1-42) had degenerated neurites, in which ganglioside and cholesterol-rich domains were localized, preceding cell death. A reduction in the amount of cholesterol by the cholesterol synthesis inhibitor compactin almost nullified the formation of amyloids by Abeta-(1-42). Our system using NGF-differentiated PC12 cells and Congo red is useful for screening inhibitors of the formation of amyloids by and cytotoxicity of Abeta.     

Physicochemical interactions of amyloid β-peptide with lipid bilayers

The aggregation and deposition onto neuronal cells of amyloid β-peptide (Aβ) is central to the pathogenesis of Alzheimer's disease. Accumulating evidence suggests that membranes play a catalytic role in the aggregation of Aβ. This article summarizes the structures and properties of Aβ in solution and the physicochemical interaction of Aβ with lipid bilayers of various compositions. Reasons for discrepancies between results by different research groups are discussed. The importance of ganglioside clusters in the aggregation of Aβ is emphasized. Finally, a hypothetical physicochemical cascade in the pathogenesis of the disease is proposed.