Far-red pentamethine cyanine dyes as fluorescent probes for the detection of serum albumins.

Benzothiazole based cyanine dyes with bridged groups in the pentamethine chain were studied as potential far-red fluorescent probes for protein detection. Spectral-luminescent properties were characterized for unbound dyes and in the presence of serum albumins (bovine (BSA), human (HSA), equine (ESA)), and globular proteins (ß-lactoglobulin, ovalbumin). We have observed that the addition of albumins leads to a significant increase in dyes fluorescence intensity. However, the fluorescent response of dyes in the presence of other globular proteins was notably lower. The value of fluorescence quantum yield for dye bearing a sulfonate group complexed with HSA amounted to 42% compared with 0.2% for the free dye. The detection limit of HSA by this dye was greater than 0.004 mg ml-1 which indicates the high sensitivity of dye to low HSA concentrations. Modelling of structure of the dyes complexes with albumin molecules was performed by molecular docking. According to these data, dyes could bind to up to five sites on the HSA molecule; the most preferable are the haemin-binding site in subdomain IB and the dye-binding site in the pocket between subdomains IA, IIA and IIIA. This work confirms that pentamethine cyanine dyes could be proposed as powerful far-red fluorescent probes applicable for highly sensitive detection of albumins.

Artemisinin modulating effect on human breast cancer cell lines with different sensitivity to cytostatics.

AIM: To explore effects of Artemisinin on a series of breast cancer cells with different sensitivity to typical cytotoxic drugs (doxorubicin - Dox; cisplatin - DDP) and to investigate possible artemisinin-induced modification of the mechanisms of drug resistance. MATERIALS AND METHODS: The study was performed on wild-type breast cancer MCF-7 cell line (MCF-7/S) and its two sublines MCF-7/Dox and MCF-7/DDP resistant to Dox and DDP, respectively. The cells were treated with artemisinin and iron-containing magnetic fluid. The latter was added to modulate iron levels in the cells and explore its role in artemisinin-induced effects. The MTT assay was used to monitor cell viability, whereas changes of expression of selected proteins participating in regulation of cellular iron homeostasis were estimated using immunocytochemical methods. Finally, relative expression levels of miRNA-200b, -320a, and -34a were examined by using qRT-PCR. RESULTS: Artemisinin affects mechanisms of the resistance of breast cancer cells towards both Dox and DDP at sub-toxic doses. The former drug induces changes of expression of iron-regulating proteins via different mechanisms, including epigenetic regulation. Particularly, the disturbances in ferritin heavy chain 1, lactoferrin, hepcidin (decrease) and ferroportin (increase) expression (р ≤ 0.05) were established. The most enhanced increase of miRNA expression under artemisinin influence were found for miRNA-200b in MCF-7/DDP cells (7.1 ± 0.98 fold change), miRNA-320a in MCF-7/Dox cells (2.9 ± 0.45 fold change) and miRNA-34a (1.7 ± 0.15 fold change) in MCF-7/S cells. It was observed that the sensitivity to artemisinin can be influenced by changing iron levels in cells. CONCLUSIONS: Artemisinin can modify iron metabolism of breast cancer cells by its cytotoxic effect, but also by inducing changes in expression of iron-regulating proteins and microRNAs (miRNAs), involved in their regulation. This modification affects the mechanisms that are implicated in drug-resistance, that makes artemisinin a perspective modulator of cell sensitivity towards chemotherapeutic agents in cancer treatment.

Oxo-Functionalized Graphene as a Cell Membrane Carrier of Nucleic Acid Probes Controlled by Aging.

We applied a fluorescein-containing oligonucleotide (ON) to probe surface properties of oxidized graphene (oxo-G) and observed that graphene-like patches are formed upon aging of oxo-G, indicated by enhanced probe binding and by FTIR spectroscopic analysis. By using a recently developed fluorogenic endoperoxide (EP) probe, we confirmed that during the aging process the amount of EPs on the oxo-G surface is reduced. Furthermore, aging was found to strongly affect cell membrane carrier properties of this material. In particular, freshly prepared oxo-G does not act as a carrier, whereas oxo-G aged for 28 days at 4 °C is an excellent carrier. Based on these data we prepared an optimized oxo-G, which has a low-defect density, binds ONs, is not toxic, and acts as cell membrane carrier. We successfully applied this material to design fluorogenic probes of representative intracellular nucleic acids 28S rRNA and ß-actin-mRNA. The results will help to standardize oxidized graphene derivatives for biomedical and bioanalytical applications.

Red light activated "caged" reagents for microRNA research.

"Caged" reagents for miRNA research (siRNA targeting EGFR, involved in miRNA maturation, and mimics of miR-20a, playing a key role in tumor formation and metastasis) were prepared. It was demonstrated that these reagents can be activated by non-toxic to cells red light both in cells and in cell free settings.

Red light-controlled polymerase chain reaction.

A 23-mer DNA "caged" at its 3'-terminus with a 9-anthracenyl moiety was prepared. It can be uncaged in the presence of photosensitizer (In(pyropheophorbide-a)chloride)-containing DNAs (9-12 mers) and upon irradiation with red light. This mixture of DNAs was used to design red-light controlled polymerase chain reaction.

Pharmacological effect of aminoferrocene in mice with L1210 leukemia.

AIM: To study the cytostatic and some biological effects of aminoferrocene using mice with L1210 lymphoid leukemia. MATERIALS AND METHODS: Experiments were performed on BDF1 male mice (DBA/2, female × C57Bl/6, male) with transplantable L1210 lymphoid leukemia. Determination of antitumor activity of Benzyl-Fc Boron (Bn), it was injected intraperitoneally 6 times daily, starting on day 2 after L1210 leukemia cell transplantation. Doses of Bn such as 26; 260 and 2600 µg/kg were used. The determination of intracellular content of cardiolipin, thiols, reactive oxygen species (ROS) and also analysis of Annexin V positivity and mitochondrial transmembrane potential (JC-1 staining) were performed with use of flow cytometry. The levels of "free iron" complexes, transferrin active forms and the rate of NO generation were measured by EPR-specroscopy. RESULTS: Six daily injections of Bn at a dose of 26 µg/kg resulted in an increased survival of mice with L1210 leukemia by 28% (p < 0.05). Bn led to an increase of apoptotic cells number and ROS amount in leukemia cells. Besides, Bn caused a decrease of cardiolipin and nonprotein thiol compounds content. The membrane electrochemical potential of cell mitochondria was decreased also after Bn administration. Studies using EPR-spectroscopy revealed a significant increase in a level of "free iron", content of transferrin active species and generation rate of NO by inducible NO-synthase in L1210 cells after aminoferrocene administration. CONCLUSION: Our data indicate that Benzyl-Fc Boron can be promising candidate for realizing a new strategy of anticancer therapy with the use of ROS-inducing agents.

Synthesis and monitored selection of nucleotide surrogates for binding T:A base pairs in homopurine-homopyrimidine DNA triple helices.

A total of 16 oligodeoxyribonucleotides of general sequence 5'-TCTTCTZTCTTTCT-3', where Z denotes an N-acyl-N-(2-hydroxyethyl)glycine residue, were prepared via solid phase synthesis. The ability of these oligonucleotides to form triplexes with the duplex 5'-AGAAGATAGAAAGA-HEG-TCTTTCTATCTTCT-3', where HEG is a hexaethylene glycol linker, was tested. In these triplexes, an 'interrupting' T:A base pair faces the Z residue in the third strand. Among the acyl moieties of Z tested, an anthraquinone carboxylic acid residue linked via a glycinyl group gave the most stable triplex, whose UV melting point was 8.4 degrees C higher than that of the triplex with 5'-TCTTCTGTCTTTCT-3' as the third strand. The results from exploratory nuclease selection experiments suggest that a combinatorial search for strands capable of recognizing mixed sequences by triple helix formation is feasible.

Monitored selection of DNA-hybrids forming duplexes with capped terminal C:G base pairs.

Reported here are the results of a search for modified oligodeoxynucleotides with a 5'-terminal cytidine residue whose affinity for target strands is enhanced by 5'-acylamido groups. These acylamido groups were envisioned to act as molecular caps that bind to the exposed terminal base pair of the duplex with the target strand. A total of 52 capped oligonucleotides of the sequence R-CGGTTGAC, where R denotes the 5'-appendage and C a 5'-amino-2',5'-dideoxycytidine residue, were tested. Among the building blocks employed to modify the 5'-amino group of the DNA strand were carboxylic acid residues, either appended directly or via an amino acid residue, and aromatic aldehydes, coupled via reductive amination. The carboxylic acids employed ranged from Fmoc-glycine to (Fmoc)(2)-vancomycin and included a number of aromatic acids and bile acids. Small libraries were subjected to MALDI-monitored nuclease selection experiments, and selected compounds were tested in UV-melting assays with target strands. Cholic acid appendages stabilized terminal C:G base pairs to the greatest extent, with melting point increases of up to 10 degrees C. Further, the cholic acid residue enhanced base pairing fidelity at the terminus, as determined in melting analyses with target strands containing a mismatched nucleobase at the 3'-terminus.

A 2'-acylamido cap that increases the stability of oligonucleotide duplexes.

[structure: see text]. Reported here is the synthesis of oligonucleotides containing a 2'-acylamido-2'-deoxyuridine residue at their 3'-terminus. Compared to control sequences bearing a thymidine residue, the quinolone-capped duplexes give higher UV melting points. In the case of (5'-ACGCGU-NA-2')2, where NA denotes a nalidixic acid residue, the melting point increase is up to 22 degrees C over that of (ACGCGT)2.

Synthesis and monitored selection of 5'-nucleobase-capped oligodeoxyribonucleotides.

Oligodeoxynucleotides bearing 5'-appendages consisting of a nucleobase and an amide linkage were prepared from 5'-amino-5'-deoxyoligonucleotides, amino acid building blocks and thymine or uracil derivatives. Small chemical libraries of 5'-modified oligonucleotides bearing the nucleobase moieties via five, three or two atom linkages were subjected to spectrometrically monitored nuclease selections to identify members with high affinity for target strands. The smallest of the appendages tested, a uracil acetic acid substituent, was found to convey the greatest duplex stabilizing effect on the octamer 5'-T*GGTTGAC-3', where T* denotes the 5'-amino-5'-deoxythymidine residue. Compared to 5'-TTGGTTGAC-3', the modified sequence 5'-u-T*GGTTGAC-3' gives a duplex with 5'-GTCAACCAA-3' that melts 4 degrees C higher. The duplex-stabilizing effect of this 5'-substituent does not require a specific residue at the 3'-terminus of the complement and the available data suggest that the uracil moiety is located in the major groove of the duplex.

Organoantimony(V) cyanoximates: synthesis, spectra and crystal structures.

A series of 25 new organoantimony(V) cyanoximates has been synthesized and studied using IR, visible, and NMR spectroscopy and X-ray analysis. Crystal structures were determined for compounds (C6H5)4Sb[ONC(CN)C(O)NH2] (1) and (C6H5)4Sb[ONC(CN)C(O)N(CH3)2] (2). Both complexes crystallized in the monoclinic space group P2(1)/c (Z = 4) with unit cell parameters (A, grad) of a = 14.921(3), b = 10.165(2), c = 17.571(7), beta = 113.26(6) for compound 1, and a = 16.415(4), b = 10.406(3), c = 17.152(3), beta = 17.152(3), beta = 117.79(2) for compound 2. For 5438 and 5056 independent reflections the refinement yielded R-factors 0.022 and 0.037 for the structures of 1 and 2, respectively. Cyanoxime anions are bound to the antimony(V) atoms in a monodentate fashion via the oxygen atoms of the oxime groups. The ligands adopt trans-anti configuration in these compounds. The coordination polyhedron in both complexes is a distorted trigonal bipyramid with the axial location of the cyanoxime ligand. A similar binding mode of other anions in synthesized organoantimony(V) complexes has been offered on the basis of the similarity of their IR spectra to those of the compounds whose structures were determined crystallographically. The exact assignment of vibrations involving the oxime group was carried out using synthesized 15N(53%), isotopomers.