Surface-enhanced Raman spectra of rhodamine 19 octadecylamide

Surface-enhanced Raman scattering (SERS) of the cationic and the neutral form of rhodamine 19 octadecylamide (R19OA) has been studied in the silver citrate colloid using NIR excitation at 1064 nm. Cationic molecules readily adsorb onto negatively charged silver nanoparticles through a positively charged xanthene part of the molecules resulting in surface enhancement of Raman scattering. Due to a lack of the positive charge in molecular structure, SERS spectrum of neutral molecules is not observed. Nevertheless, a broad band appearing at 1240 cm^?1 in the spectrum of the cationic form indicates conversion of the cationic into the neutral species occurring close to the silver surface. The observed band most likely arises from a vibration of the ring formed in the molecular structure after conversion, but before complete desorption of the neutral molecules from the metal surface. Upon addition of HCl and NaOH in the silver sol, equilibrium is shifted toward the cationic and the neutral form of R19OA, respectively, followed by corresponding changes in the Raman spectrum. In addition, FT-SERS spectra of two rhodamine dyes, rhodamine 19 (R19) and rhodamine 6G (R6G), that are structurally related to R19OA, have been studied under the same experimental conditions for comparison.     

Tetracationic Bis-Triarylborane 1,3-Butadiyne as a Combined Fluorimetric and Raman Probe for Simultaneous and Selective Sensing of Various DNA,RNA, and Proteins

A bis-triarylborane tetracation (4-Ar₂B-3,5-Me₂C₆H₂)-C≡C−C≡C-(3,5-Me₂C₆H₂-4-BAr₂ [Ar=(2,6-Me₂-4-NMe₃-C₆H₂)⁺] ( 2⁴⁺ ) shows distinctly different behaviour in its fluorimetric response than that of our recently published bis-triarylborane 5-(4-Ar₂B-3,5-Me₂C₆H₂)-2,2′-(C₄H₂S)₂–5′-(3,5-Me₂C₆H₂-4-BAr₂) ( 3⁴⁺ ). Single-crystal X-ray diffraction data on the neutral bis-triarylborane precursor 2 N confirm its rod-like dumbbell structure, which is shown to be important for DNA/RNA targeting and also for BSA protein binding. Fluorimetric titrations with DNA/RNA/BSA revealed the very strong affinity of 2⁴⁺ and indicated the importance of the properties of the linker connecting the two triarylboranes. Using the butadiyne rather than a bithiophene linker resulted in an opposite emission effect (quenching vs. enhancement), and 2⁴⁺ bound to BSA 100 times stronger than 3⁴⁺ . Moreover, 2⁴⁺ interacted strongly with ss-RNA, and circular dichroism (CD) results suggest ss-RNA chain-wrapping around the rod-like bis-triarylborane dumbbell structure like a thread around a spindle, a very unusual mode of binding of ss-RNA with small molecules. Furthermore, 2⁴⁺ yielded strong Raman/SERS signals, allowing DNA or protein detection at ca. 10 nm concentrations. The above observations, combined with low cytotoxicity, efficient human cell uptake and organelle-selective accumulation make such compounds intriguing novel lead structures for bio-oriented, dual fluorescence/Raman-based applications.     

DNA binding,antibacterial and antifungal activities of copper(II) complexes with some S-alkenyl derivatives of thiosalicylic acid

The biological activities of two binuclear copper(II) complexes containing S-alkenyl derivatives of thiosalicylic acid are reported [alkenyl = propenyl (L1), isobutenyl (L2)]. The structure of the complex with the S-isobutenyl derivative (C2) was confirmed by single-crystal X-ray structure analysis, which revealed that the structure consists of centrosymmetric, dinuclear complex molecules [Cu₂(S-i-butenyl-thiosal)₄(DMSO)₂] containing two Cu(II) centers bridged by four S-isobutyl-thiosalicylate ligands in a paddle-wheel type structure. The Cu(II) atom is situated in a distorted square-pyramidal environment formed by carboxylate oxygen atoms in the basal plane and a DMSO ligand in the axial position. The reactivities of the complexes toward guanosine-5′-monophosphate (5′-GMP) were investigated. Complex C2 ([Cu₂(S-i-butenyl-thiosal)₄(H₂O)₂]) reacted more rapidly with 5′-GMP than complex C1. The interactions of complexes C1 and C2 with calf thymus DNA (CT-DNA) were examined by absorption (UV–Vis) and emission spectral studies (ethidium bromide displacement studies), revealing good DNA interaction abilities. The antimicrobial activities of the free ligands and their complexes were tested by microdilution method, and both minimal inhibitory and microbicidal concentrations were determined. All the tested substances demonstrated selective and moderate antibacterial activity on gram-positive bacteria, but low antibacterial activity on gram-negative bacteria. Also, the tested substances demonstrated low antifungal activity.     

Co(III) complex with (E)-2-(2-(pyridine-2-ylmethylene)hydrazinyl)-4-(4-tolyl)-1,3-thiazole: structure and activity against 2-D and 3-D cancer cell models

Co(III) complex with a 2-hydrazonylthiazole ligand was synthesized and characterized by single-crystal X-ray diffraction. In the inner sphere of the complex, two monoionic ligands are coordinated tridentately forming octahedral geometry around Co(III). Activity of the complex was investigated on MCF-7 breast cancer cell line, with cisplatin (CDDP) as a reference compound. Results showed that after 24-h incubation, Co(III) complex revealed stronger cytotoxic activity compared to CDDP. Treatment of MCF-7 3-D cell model with the complex at 10 μM concentration achieved complete suppression of spheroid growth in almost the same extent as at 100 μM. In combination treatments on MCF-7 spheroids, the complex acted synergistically with CDDP, while additive interaction type was achieved when the complex was applied together with paclitaxel.     

Differentiation of black,green, herbal and fruit bagged teas based on multi-element analysis using inductively-coupled plasma atomic emission spectrometry

In the present paper, multi-element characterisation of 26 bagged teas was carried out using inductively-coupled plasma atomic emission spectrometry. Na, K, Ca and Mg were the metals with major contents. Among the essential elements, Fe and Zn were the most abundant, followed by Se, Cu, Mo and Cr. The tea bag samples also contained significant contents of Mn and Al. The chemometric techniques of linear correlation analysis, principal component analysis (PCA) and cluster analysis (CA) were used for differentiation of the tea bag samples according to their metal content. The samples analysed were classified into four groups by PCA and CA. The first group includes hibiscus, nettle, mint, rtanj tea, thyme, bearberry and sage. Green and black teas are in the second group. The third group contains strawberry, lime, pineapple, pomegranate, elder, blueberry, milfoil, apricot and chamomile. Exotic fruits, sweet cherry, forest fruits, apple, St John’s wort, rose hips, cherry and raspberry are in the fourth group.     

Influence of Transverse Shear on Stochastic Instability of the Elastic Beam

In the case when Kirchhoff–Love hypotheses do not give satisfactory results, we have to take the rotatory inertia and transverse shear into account. This paper studies the elastic beam subjected to stochastic axial load, when transverse shear is taken into account. By using the direct Liapunov method, the bounds of the almost sure instability of beams as the function of the damping coefficient, variance of the stochastic force, geometric parameters, mode number, section shape factor and intensity of the deterministic component of axial loading, are obtained. Calculations are performed for the Gaussian process with zero mean and variance ², as well as for the harmonic process with amplitude A.     

Study of the structure,prooxidative, and cytotoxic activity of some chelate copper(II) complexes

The six chelate N,O-copper(II) complexes were synthesised starting from salicylaldehyde anil Schiff bases, as ligands. Their structure is elucidated using experimental and theoretical tools. In vitro biological activities, i.e. cytotoxic and prooxidative effects against human epithelial mammary gland/breast metastatic carcinoma MDA-MB-231, epithelial colorectal carcinoma HCT-116, and foetal lung fibroblast healthy MRC-5 cell lines of investigated compounds are also determined. Complexes Cu-1, Cu-6, and especially Cu-7 showed significant cytotoxic effects, with IC₅₀ values comparable with effects of positive control CisPt. In addition, investigated complexes induced extreme oxidative and nitrosative stress in all treated cell lines. The most prominent effect is observed on HCT-116 cells, and on MRC-5 cells, while MDA-MB-231 cells showed higher resistance to the investigated cell lines, giving us direction towards the substances with more specific selectivity.     

The thermal susceptibility of poly(chloroethyl methacrylates)

The non-oxidative thermal degradation kinetics and mechanism of poly(2-monochloro, 2, 2-dichloro and 2, 2, 2, -trichloroethyl methacrylates) were studied. The influence of the antioxidant IRGA-NOX 1010 on the thermal degradation of the monochloroethyl derivative was also investigated. Initial hydrolysis data on the major degradation products, the corresponding monomers, were obtained.     

Spectrophotometric determination of furosemide as its Fe(III) complex in pharmaceutical preparations

A new spectrophotometric method for determination of furosemide is described. The method is based on the reaction of furosemide with ferric chloride in pH range 5.2–6.2 and producing a red water-soluble (2 1) complex with maximum absorbance at 513 nm. By applying the methods of Sommer and Job involving non-equimolar solutions the conditional stability constant of the complex, at the optimum pH of 5.7, and ionic strength =0.1M, is found to be 10^6.5. Beer's law is obeyed up to 8 mmol/l furosemide concentration. The detection limit of the method is 0.03 mg/ml. The relative standard deviation (n=20) is 1.03% and relative error of the method is 0.5%. The proposed method was found to be suitable for the accurate and reproducible analysis of furosemide in tablets and ampoules, what is pointed by high recovery values 98.78–100.6% and low values of relative standard deviations 1.68–2.08%. The results obtained show that the method is applicable to routine analysis.