Maria Strianese

A FRET Enzyme-Based Probe for Monitoring Hydrogen Sulfide

Fluorescently labeled cobalt peptide deformylase (Co-PDF) can be efficiently used as a fluorescence-resonance-energy-transfer-based sensing device for hydrogen sulfide (H(2)S). The proof of concept of our sensor system is substantiated by spectroscopic, structural, and theoretical results. Monohydrogen sulfide coordination to Co-PDF and Ni-PDF was verified by X-ray crystallography. Density functional theory calculations were performed to gain insight into the characteristics of the coordination adduct between H(2)S and the cobalt cofactor in Co-PDF.

Selective detection of ATP and ADP in aqueous solution by using a fluorescent zinc receptor

We report on the successful use of a new zinc complex for the selective fluorescent detection of ADP and ATP in water. This is achieved by the complementary coordination of the phosphate groups to the metal centre and hydrogen bonding of the adenosine with the coordinated ligand.

Myoglobin as a New Fluorescence Probe to Sense H2S

A new, fast, simple and cost-effective sensing device for monitoring H(2)S has been developed. Proof-of-principle results showing that a commercial and cheap Myoglobin (Mb) can be successfully used as a biological probe for a fluorescence biosensor for H(2)S detection are reported. The two different commercial labels Cy3 and Atto620 were selected for this study. A high selectivity for detecting H(2)S against other thiols was found. The applicability of the proposed sensing system was successfully explored not only in solution but also when applied in the form of a solid state device.

Phosphido pincer complexes of platinum: synthesis, structure and reactivity

A series of platinum(II) complexes supported by the tridentate bis(phosphine)phosphido ligand bis(2-diisopropylphosphinophenyl)phosphide) [(i)Pr-PPP] have been synthesized and characterized (1-4). X-Ray structural studies of [(i)Pr-PPP]PtCl (1) and [(i)Pr-PPP]PtCH(3) (3) complexes show meridional [(i)Pr-PPP] ligands around approximately square-planar platinum centers. Structural data and NMR analysis highlight a strong trans influence for the phosphido phosphorous donor, comparable to that of the anionic aryl carbon of the classic PCP pincer complexes. A series of thermally stable [PPP]Pt(IV) compounds, including [PPP]Pt(CH(3))(2)X [X = I (5) and SbF(6) (6)], were also synthesized. The study of the binding affinity of SO(2) and NO to complex 1 has also been addressed.

Therapeutic potential of a pyridoxal‐based vanadium(IV) complex showing selective cytotoxicity for cancer versus healthy cells

Vanadium compounds can exert anticancer effects, partly due to inhibition of tyrosine phosphatases. Here, we report the effect of N,N′‐ethylenebis (pyridoxylideneiminato) vanadium (IV) complex (Pyr2enV(IV)), that induced 93% and 57% of cell mortality in A375 (human melanoma) and A549 (human lung carcinoma) cells, respectively; the mortality was <24% in other cancer cell lines and in human normal epidermal keratinocytes, lung cells and peripheral blood mononuclear cells. The mechanism of Pyr2enV(IV) effect relied on apoptosis induction; this was triggered by ROS increase, followed by mitochondrial membrane depolarization. Indeed, the addition of N‐acetyl cysteine to cell cultures abated Pyr2enV(IV)‐induced apoptosis. These results disclose the pro‐apoptotic activity of Pyr2enV(IV) and its mechanism, relying on intracellular ROS increase. J. Cell. Physiol. 228: 2202–2209, 2013.

Heteroscorpionate-based Co2+, Zn2+, and Cu2+ complexes: coordination behavior, aerobic oxidation, and hydrogen sulfide detection.

The coordination behavior and reactivity of the phenol-substituted bis(pyrazolyl)methane ligands, (3,5-(t)Bu(2)-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L1-H) and 2-phenol-bis(3,5-Me(2)-pyrazol-1-yl)methane (L2-H) have been investigated in the metal complexes (L1-H)CoCl(2) (1), (L1-H)ZnCl(2) (2), (L3)CuCl(2) (3), (L2)(2)Co(2)Cl(2) (4) (L2-H)ZnCl(2) (5), and (L2-H)CuCl(2)·H(2)O (6). The mononuclear tetrahedral cobalt complex 1 was isolated and fully characterized by X-ray single crystal diffraction and (1)H NMR spectroscopy and relaxometry. The neutral L1-H is κ(2)-coordinated to the metal center whereas the not coordinated hydroxy-phenyl group is involved in extended intermolecular hydrogen bonds. Aerobic oxidation of L1-H was observed in the reaction of this ligand with CuCl(2) to yield the para-quinone derivative L3 (L3 = 2-(t)Bu-6-(bis(3,5-Me(2)-pyrazol-1-yl)methyl)cyclohexa-2,5-diene-1,4-dione). Upon oxidation L3 resulted κ(2)-coordinated to the tetrahedral Cu(II) metal center, affording 3. The reaction of L2-H with CoCl(2)·6H(2)O produced the elimination of 1 equiv of hydrochloric acid and the formation of the binuclear complex 4 in which one cobalt is in an octahedral environment featuring two κ(3)-coordinated deprotonated ligands whereas the second cobalt center is detected in tetrahedral coordination geometry, bound to the octahedral cobalt via two phenoxo bridging moieties. Interestingly L2-H, (3-(t)Bu-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L4-H), or (5-(t)Bu-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L5-H) were not oxidized in the reaction with CuCl(2). The reaction of the ligand L2-H with ZnCl(2) and CuCl(2)·2H(2)O yielded the κ(2)-coordinated tetrahedral complex 5 and the square planar complex 6, respectively. The application of the cobalt complex 1 as molecular dosimeter for H(2)S was explored and compared to that of the zinc analogue 2. Density functional theory (DFT) calculations and NMR experiments to assess the possible mechanisms of H(2)S detection by both 1 and 2 are also described.

A protein-based oxygen biosensor for high-throughput monitoring of cell growth and cell viability

Fluorescently labeled hemocyanin has been previously proposed as an oxygen sensor. In this study, we explored the efficacy of this biosensor for monitoring the biological oxygen consumption of bacteria and its use in testing bacterial cell growth and viability of Escherichia coli, Pseudomonas aeruginosa, Paracoccus denitrificans, and Staphylococcus simulans. Using a microwell plate, the time courses for the complete deoxygenation of samples with different initial concentrations of cells were obtained and the doubling times were extracted. The applicability of our fluorescence-based cell growth assay as an antibacterial drug screening method was also explored. The results provide a proof-of-principle for a simple, quantitative, and sensitive method for high-throughput monitoring of prokaryotic cell growth and antibiotic susceptibility screening.

Fluorescence-Based Biosensors

The field of optical sensors has been a growing research area over the last three decades. A wide range of books and review articles has been published by experts in the field who have highlighted the advantages of optical sensing over other transduction methods. Fluorescence is by far the method most often applied and comes in a variety of schemes. Nowadays, one of the most common approaches in the field of optical biosensors is to combine the high sensitivity of fluorescence detection in combination with the high selectivity provided by ligand-binding proteins. In this chapter we deal with reviewing our recent results on the implementation of fluorescence-based sensors for monitoring environmentally hazardous gas molecules (e.g. nitric oxide, hydrogen sulfide). Reflectivity-based sensors, fluorescence correlation spectroscopy-based (FCS) systems, and sensors relying on the enhanced fluorescence emission on silver island films (SIFs) coupled to the total internal reflection fluorescence mode (TIRF) for the detection of gliadin and other prolamines considered toxic for celiac patients are also discussed herein.

Organometallic sulfur complexes: reactivity of the hydrogen sulfide anion with cobaloximes

The reaction of alkylcobaloxime [Co(dmgH)2(CH2CH3)(py)] (1) (dmgH = the anion of dimethyl-glyoxime) with KSH in water solution resulted in the selective displacement of the pyridine axial ligand affording the derivative K[Co(dmgH)2(CH2CH3)(SH)] (2). An 1H–1H EXSY experiment revealed that the substitution is reversible and occurs in a slow exchange regime. Attempts to grow crystals of the HS− adduct led to isolation of a rare example of the unexpected trisulfido-bridged dinuclear complex K2[Co2(dmgH)2(CH2CH3)2(μ-S3)]. It was shown that the glyoximato ligands provided the metal centre with a coordination environment quite robust to prevent decomposition and constitute a suitable platform for developing the chemistry of organometallic complexes bearing hydrogensulfido or oligosulfido ligands.

A FRET-based biosensor for NO detection.

In this paper we explore the use of fluorescently labeled cytochrome c peroxidase (CcP) from bakers yeast for monitoring nitric oxide (NO) down to the sub-micromolar level, by means of a FRET (Förster Resonance Energy Transfer) mechanism. The binding affinity constant (K(d)) for the NO binding to CcP was determined to be 10+/-1.5 microM. The rate of NO dissociation from the CcP (k(off)) and the second order rate constant for the NO association (k(on)) were found to be 0.22+/-0.08 min(-1) and 0.024+/-0.002 microM(-1) min(-1) respectively. The immobilization of fluorescently labeled CcP into a polymeric matrix for use in a solid state NO sensing device was also explored. The results provide proof-of-principle that labeled CcP can be successfully implemented in a fast, simple, quantitative and sensitive NO sensing device.