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In contrast to many other water birds, the Great Cormorant, Phalacrocorax carbo (Phalacrocoracidae), shows a typical wing-spreading behavior after diving. This behavior has been linked to the partial wettability of the Cormorant’s feathers based on the unusual structure of the contour feathers. Close to the rachis, these feathers have a closed vane with very densely spaced barbs but have an open vane in more peripheral feather parts. To investigate whether the wettability is connected to the composition of the uropygial gland secretion that is often linked to water repellency of bird feathers, we analyzed the gland secretions of the Great Cormorant and, for comparison, of the Muscovy Duck, Cairina moschata (Anatidae). Using the mass spectrometry techniques, atmospheric solids analysis probe-atmospheric pressure chemical ionization-mass spectrometry (ASAP-APCI-MS) and gas chromatography/mass spectrometry (GC/MS), significant differences in the chemical composition of the secretions were revealed. The Cormorant showed a highly diverse mixture of more than 1000 compounds consisting of methyl-branched aliphatic carboxylic esters with large chain length variability. In contrast, the duck’s secretion is dominated by the two esters octadecyl and eicosyl 2,4,6-trimethyloctanoate. Water contact angle measurements of the secretions showed that the secretion of the Muscovy Duck has higher water repellency than that of the Great Cormorant. Nevertheless, contact angle measurements of feathers before and after removing of feather waxes indicate that these waxes, likely consisting of the uropygial gland secretions, did not influence water repellency of the feathers to a large degree.

In the synthesis of chiral molecules, the incorporation of enantioselective enzymatic conversions within the synthetic route often presents a useful approach. For the substitution of a chemical step with an enzymatic reaction, however, the complete synthetic route leading to and from this reaction needs to be considered carefully. An integrated approach, taking the possibilities and challenges of both types of conversions into account, can give access to chemo-enzymatic processes with great potential for effective synthesis strategies. We here report on the synthesis of enantiopure flurbiprofen using arylmalonate decarboxylase (AMDase, EC 4.1.1.76) in a chemo-enzymatic approach. Interestingly, practical considerations required shifting the enzymatic step to an earlier position in the synthetic route than previously anticipated. Engineered enzyme variants made it possible to obtain both (R)- and (S)-enantiomers of the target compound in excellent optical purity (>99%ee). The presented results underline that enzymes are most useful when they fit in a synthetic route, and that the optimization of biocatalytic steps and the planning of synthetic routes should be an integrated process.

An enzymatic cascade from ω-amino amino acids towards monohydroxylated α,ω-diamines gives highly interesting materials for processing into fine chemicals. With two simple UV-vis spectroscopy-based screening methods, enzyme candidates with a compatibility window to perform a three-enzyme cascade from lysine and ornithine to the desired products were identified. The results give first insight into the feasibility of the desired cascade and put handles on future reaction engineering tasks.

Styrene and indole monooxygenases (SMO and IMO) are two-component flavoprotein monooxygenases composed of a nicotinamide adenine dinucleotide (NADH)-dependent flavin adenine dinucleotide (FAD)-reductase (StyB or IndB) and a monooxygenase (StyA or IndA). The latter uses reduced FAD to activate oxygen and to oxygenate the substrate while releasing water. We circumvented the need for the reductase by direct FAD reduction in solution using the NAD(P)H-mimic 1-benzyl-1,4-dihydronicotinamide (BNAH) to fuel monooxygenases without NADH requirement. Herein, we report on the hitherto unknown solvent tolerance for the indole monooxygenase from \(\textit {Gemmobacter nectariphilus}\) DSM15620 (\(\it Gn\)IndA) and the styrene monooxygenase from \(\textit {Gordonia rubripertincta}\) CWB2 (\(\it Gr\)StyA). These enzymes were shown to convert bulky and rather hydrophobic styrene derivatives in the presence of organic cosolvents. Subsequently, BNAH-driven biotransformation was furthermore optimized with regard to the applied cosolvent and its concentration as well as FAD and BNAH concentration. We herein demonstrate that \(\it Gn\)IndA and \(\it Gr\)StyA enable selective epoxidations of allylic double bonds (up to 217 mU \(mg^{−1}\)) in the presence of organic solvents such as tetrahydrofuran, acetonitrile, or several alcohols. Notably, \(\it Gn\)IndA was found to resist methanol concentrations up to 25 vol.%. Furthermore, a diverse substrate preference was determined for both enzymes, making their distinct use very interesting. In general, our results seem representative for many IMOs as was corroborated by in silico mutagenetic studies.

Amino groups derived from naturally abundant amino acids or (di)amines can be used as “shuttles” in nature for oxygen transfer to provide intermediates or products comprising N-O functional groups such as N-hydroxy, oxazine, isoxazolidine, nitro, nitrone, oxime, C-, S-, or N-nitroso, and azoxy units. To this end, molecular oxygen is activated by flavin, heme, or metal cofactor-containing enzymes and transferred to initially obtain N-hydroxy compounds, which can be further functionalized. In this review, we focus on flavin-dependent N-hydroxylating enzymes, which play a major role in the production of secondary metabolites, such as siderophores or antimicrobial agents. Flavoprotein monooxygenases of higher organisms (among others, in humans) can interact with nitrogen-bearing secondary metabolites or are relevant with respect to detoxification metabolism and are thus of importance to understand potential medical applications. Many enzymes that catalyze N-hydroxylation reactions have specific substrate scopes and others are rather relaxed. The subsequent conversion towards various N-O or N-N comprising molecules is also described. Overall, flavin-dependent N-hydroxylating enzymes can accept amines, diamines, amino acids, amino sugars, and amino aromatic compounds and thus provide access to versatile families of compounds containing the N-O motif. Natural roles as well as synthetic applications are highlighted. Key points• N-O and N-N comprising natural and (semi)synthetic products are highlighted.• Flavin-based NMOs with respect to mechanism, structure, and phylogeny are reviewed.• Applications in natural product formation and synthetic approaches are provided.

Ene‐reductases allow regio‐ and stereoselective reduction of activated C=C double bonds at the expense of nicotinamide adenine dinucleotide cofactors [NAD(P)H]. Biological NAD(P)H can be replaced by synthetic mimics to facilitate enzyme screening and process optimization. The ene‐reductase FOYE‐1, originating from an acidophilic iron oxidizer, has been described as a promising candidate and is now being explored for applied biocatalysis. Biological and synthetic nicotinamide cofactors were evaluated to fuel FOYE‐1 to produce valuable compounds. A maximum activity of (319.7±3.2) U mg−1 with NADPH or of (206.7±3.4) U mg−1 with 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) for the reduction of N‐methylmaleimide was observed at 30 °C. Notably, BNAH was found to be a promising reductant but exhibits poor solubility in water. Different organic solvents were therefore assayed: FOYE‐1 showed excellent performance in most systems with up to 20 vol% solvent and at temperatures up to 40 °C. Purification and application strategies were evaluated on a small scale to optimize the process. Finally, a 200 mL biotransformation of 750 mg (R)‐carvone afforded 495 mg of (2R,5R)‐dihydrocarvone (>95 % ee), demonstrating the simplicity of handling and application of FOYE‐1., Enantioselective hydrogenation: Ene‐reductases (ERs, OYEs) are versatile biocatalysts for selective hydrogenation of activated C=C double bonds. FOYE‐1 was characterized with respect to solvent stability for the conversion of (R)‐carvone into (2R,5R)‐dihydrocarvone at the expense of the synthetic nicotinamide cofactor 1‐benzyl‐1,4‐dihydronicotinamide, the activity of which is compared with that of the natural electron donor NAD(P)H.

Tyrosine kinase receptors are one of the main targets in cancer therapy. They play an essential role in the modulation of growth factor signaling and thereby inducing cell proliferation and growth. Tyrosine kinase inhibitors such as neratinib bind to EGFR and HER2 receptors and exhibit antitumor activity. However, little is known about their detailed cellular uptake and metabolism. Here, we report for the first time the intracellular spatial distribution and metabolism of neratinib in different cancer cells using label‐free Raman imaging. Two new neratinib metabolites were detected and fluorescence imaging of the same cells indicate that neratinib accumulates in lysosomes. The results also suggest that both EGFR and HER2 follow the classical endosome lysosomal pathway for degradation. A combination of Raman microscopy, DFT calculations, and LC‐MS was used to identify the chemical structure of neratinib metabolites. These results show the potential of Raman microscopy to study drug pharmacokinetics.

Processing of lignin provides access to mono-aromatic compounds with a styrene-like structure. The vinyl sidechain can be attacked by monooxygenases, such as styrene or indole monooxygenases, to yield enantiopure epoxides. The obtained epoxides can be converted into valuable products, either enzyme- or non-enzyme driven. This provides access to drug-like molecules and technically relevant synthesis precursors. Herein, we report the setup of a simple screening strategy for useful epoxidases.

Biocatalytic (S)-naproxen synthesis using an (S)-selective arylmalonate decarboxylase mutant (AMDase G74C/M159L/C188G/V43I/A125P/V156L, AMDase-CLGIPL) exposes a promising environmentally friendly alternative to conventional chemical synthesis strategies. The reaction progress of naproxen synthesis catalyzed by AMDase-CLGIPL covalently immobilized onto a robust acrylate carrier was investigated with respect to reaction engineering. Kinetic characterization of the immobilized enzyme reveals a KM value of 22.1 ± 0.1 mM in the naproxen malonate conversion and an inhibiting effect of the produced naproxen with a Ki of 26.3 ± 1.4 mM. However, an effective process can be realized without in situ product removal yielding (S)-naproxen with an ee of 99%. By optimizing the product work-up, an isolated yield of 92% was achieved with total turnover numbers between 83 000 and 107 000 in five repetitive batches. Furthermore, process monitoring with in-line Raman spectroscopy was successfully applied to analyze the reaction progress with a root mean square error of prediction of 0.8 mM (corresponding to 4%).

Platinum(II) complexes with different cinnamic acid derivatives as ligands were investigated for their ability to inhibit the aggregation process of amyloid systems derived from Aβ, Yeast Prion Protein Sup35p and the C-terminal domain of nucleophosmin 1. Thioflavin T binding assays and circular dichroism data indicate that these compounds strongly inhibit the aggregation of investigated peptides exhibiting IC50 values in the micromolar range. MS analysis confirms the formation of adducts between peptides and Pt(II) complexes that are also able to reduce amyloid cytotoxicity in human SH-SY5Y neuroblastoma cells. Overall data suggests that bidentate ligands based on β-hydroxy dithiocinnamic esters can be used to develop platinum or platinoid compounds with anti-amyloid aggregation properties.

Platinum(II) complexes with different cinnamic acid derivatives as ligands were investigated for their ability to inhibit the aggregation process of amyloid systems derived from Aβ, Yeast Prion Protein Sup35p and the C-terminal domain of nucleophosmin 1. Thioflavin T binding assays and circular dichroism data indicate that these compounds strongly inhibit the aggregation of investigated peptides exhibiting IC50 values in the micromolar range. MS analysis confirms the formation of adducts between peptides and Pt(II) complexes that are also able to reduce amyloid cytotoxicity in human SH-SY5Y neuroblastoma cells. Overall data suggests that bidentate ligands based on β-hydroxy dithiocinnamic esters can be used to develop platinum or platinoid compounds with anti-amyloid aggregation properties.

Die Kombination von Enzymen mit herkommlichen Katalysatoren ermoglicht die Verbindung hoher Selektivitat ersterer mit der Vielseitigkeit letzterer. Eine grose Herausforderung dieses Ansatzes besteht in den sehr unterschiedlichen optimalen Reaktionsbedingungen beider Katalysatortypen. Hier kombinieren wir eine Cofaktor-freie Decarboxylase mit einem [Ru]-Metathesekatalysator zur Herstellung hochwertiger Antioxidantien aus biobasierten Vorstufen. Da geeignete [Ru]-Komplexe keine zufriedenstellende Aktivitat unter wassrigen Bedingungen zeigten, erforderte die Reaktion ein organisches Losungsmittel, das seinerseits die enzymatische Aktivitat erheblich senkte. Durch das Einkapseln des Enzyms in einer Gelmatrix konnte die Decarboxylierung in reinem organischem Losungsmittel durchgefuhrt werden, und nach einem intermediaren Trocknungsschritt war die Metathese leicht moglich. Eine sequenzielle Ein-Topf-Reaktionskaskade nach diesem Muster lieferte das Antioxidans 4,4′-Dihydroxystilben in 90 % Gesamtausbeute.

Eine in Cyanobakterien exprimierte, rekombinante Enoat-Reduktase wurde fur die lichtkatalysierte, enantioselektive Reduktion von C=C-Bindungen genutzt. Dabei ermoglicht die Kopplung von Oxidoreduktasen an die naturliche Photosynthese eine durch Wasseroxidation angetriebene asymmetrische Synthese. Durch den Verzicht auf zusatzliche Cosubstrate als Elektronendonoren wird die Bildung unerwunschter Nebenprodukte gemindert und die Atomokonomie der Reaktion erhoht. Die Verfugbarkeit von NADPH und die Menge an aktivem Enzym in der Zelle sind entscheidende Faktoren fur die Produktbildung. Die Effizienz der Reaktion ist mit derjenigen typischer Ganzzell-Biotransformationen in E. coli vergleichbar: Unter optimierten Bedingungen wurden 100 mg prochirales 2-Methylmaleimid zu enantiomerenreinem 2-Methylsuccinimid (99 % ee, 80 % Ausbeute an isoliertem Produkt) reduziert. Die hohen Produktausbeuten und die exzellente Enantiomerenreinheit durch den Einsatz rekombinanter Cyanobakterien in einer lichtgetriebenen Ganzzell-Biotransformation ergeben einen einfachen und allgemein anwendbaren Syntheseansatz.

The bacterial decarboxylase (AMDase) catalyzes the enantioselective decarboxylation of prochiral arylmalonates with high enantioselectivity. Although this reaction would provide a highly sustainable synthesis of active pharmaceutical compounds such as flurbiprofen or naproxen, competing spontaneous decarboxylation has so far prevented the catalytic application of AMDase. Here, we report on reaction engineering and an alternate protection group strategy for the synthesis of these compounds that successfully suppresses the side reaction and provides pure arylmalonic acids for subsequent enzymatic conversion. Protein engineering increased the activity of the synthesis of the (S)- and (R)-enantiomers of flurbiprofen. These results demonstrated the importance of synergistic effects in the optimization of this decarboxylase. The asymmetric synthesis of both enantiomers in high optical purity (>99 %) and yield (>90 %) can be easily integrated into existing industrial syntheses of flurbiprofen, thus providing a sustainable method for the production of this important pharmaceutical ingredient.

Arylmalonate decarboxylase (AMDase) catalyzes the cofactor‐free asymmetric decarboxylation of prochiral arylmalonic acids and produces the corresponding monoacids with rigorous R selectivity. Alteration of catalytic cysteine residues and of the hydrophobic environment in the active site by protein engineering has previously resulted in the generation of variants with opposite enantioselectivity and improved catalytic performance. The substrate spectrum of AMDase allows it to catalyze the asymmetric decarboxylation of small methylvinylmalonic acid derivatives, implying the possibility to produce short‐chain 2‐methylalkanoic acids with high optical purity after reduction of the nonactivated C=C double bond. Use of diimide as the reductant proved to be a simple strategy to avoid racemization of the stereocenter during reduction. The developed chemoenzymatic sequential cascade with use of R‐ and S‐selective AMDase variants produced optically pure short‐chain 2‐methylalkanoic acids in moderate to full conversion and gave both enantiomers in excellent enantiopurity (up to 83 % isolated yield and 98 % ee).

Correction for ‘Reactions of metallodrugs with proteins: selective binding of phosphane-based platinum(ii) dichlorides to horse heart cytochrome c probed by ESI MS coupled to enzymatic cleavage’ by Carolin Mügge et al., Metallomics, 2011, 3, 987–990.

All protein engineering studies include the stage of identifying and characterizing variants within a mutant library by employing a suitable assay or selection method. A large variety of different assay approaches for different enzymes have been developed in the last few decades, and the throughput performance of these assays vary considerably. Thus, the concept of a protein engineering study must be adapted to the available assay methods. This introductory review chapter describes different assay concepts on selected examples, including selection and screening approaches, detection of pH and cosubstrate changes, coupled enzyme assays, methods using surrogate substrates and selective derivatization. The given examples should guide and inspire the reader when choosing and developing own high-throughput screening approaches.

All protein engineering studies include the stage of identifying and characterizing variants within a mutant library by employing a suitable assay or selection method. A large variety of different assay approaches for different enzymes have been developed in the last few decades, and the throughput performance of these assays vary considerably. Thus, the concept of a protein engineering study must be adapted to the available assay methods. This introductory review chapter describes different assay concepts on selected examples, including selection and screening approaches, detection of pH and cosubstrate changes, coupled enzyme assays, methods using surrogate substrates and selective derivatization. The given examples should guide and inspire the reader when choosing and developing own high-throughput screening approaches.

Oxygenic phototrophs frequently encounter environmental conditions that result in intracellular energy crises. Growth of the unicellular green alga Chlamydomonas reinhardtii in hypoxia in the light depends on acclimatory responses of which the induction of photosynthetic cyclic electron flow is essential. The microalga cannot grow in the absence of molecular oxygen (O2 ) in the dark, although it possesses an elaborate fermentation metabolism. Not much is known about how the microalga senses and signals the lack of O2 or about its survival strategies during energy crises. Recently, nitric oxide (NO) has emerged to be required for the acclimation of C. reinhardtii to hypoxia. In this study, we show that the soluble guanylate cyclase (sGC) CYG12, a homologue of animal NO sensors, is also involved in this response. CYG12 is an active sGC, and post-transcriptional down-regulation of the CYG12 gene impairs hypoxic growth and gene expression in C. reinhardtii. However, it also results in a disturbed photosynthetic apparatus under standard growth conditions and the inability to grow heterotrophically. Transcriptome profiles indicate that the mis-expression of CYG12 results in a perturbation of responses that, in the wild-type, maintain the cellular energy budget. We suggest that CYG12 is required for the proper operation of the photosynthetic apparatus which, in turn, is essential for survival in hypoxia and darkness.

Several linear β-enamino ketone ligands and their corresponding bischelate PdII complexes bearing various combinations of methyl and trifluoromethyl groups at the chelating center as well as peripheral hydrocarbon and perfluorinated side chains were prepared. The effect of these structural modifications on the thermotropic liquid-crystalline behavior of both the ligands and the corresponding metal complexes was studied. The relationships between the molecular structures and the corresponding thermal properties are discussed. As expected, the persistence of liquid-crystalline behavior was highly sensitive to both applied structural manipulations. On the one hand, increased steric congestion around the chelating moiety clearly appears detrimental to the retention of mesomorphism. On the other hand, perfluorinated chains at the molecular extremity can occasionally restore it. Therefore, the regulation of the balance between both structural parameters permits a precise control of the mesomorphic properties of the compounds.

The enzyme arylmalonate decarboxylase (AMDase) enables the selective synthesis of enantiopure (S)-arylpropinates in a simple single-step decarboxylation of dicarboxylic acid precursors. However, the poor enzyme stability with a half-life time of about 1.2 h under process conditions is a serious limitation of the productivity, which results in a need for high catalyst loads. By immobilization on an amino C2 acrylate carrier the operational stability of the (S)-selective AMDase variant G74C/M159L/C188G/V43I/A125P/V156L was increased to a half-life of about 8.6 days, which represents a 158-fold improvement. Further optimization was achieved by simple immobilization of the cell lysate to eliminate the cost- and time intensive enzyme purification step.

A recombinant enoate reductase was expressed in cyanobacteria and used for the light-catalyzed, enantioselective reduction of C=C bonds. The coupling of oxidoreductases to natural photosynthesis allows asymmetric syntheses fueled by the oxidation of water. Bypassing the addition of sacrificial cosubstrates as electron donors significantly improves the atom efficiency and avoids the formation of undesired side products. Crucial factors for product formation are the availability of NADPH and the amount of active enzyme in the cells. The efficiency of the reaction is comparable to typical whole-cell biotransformations in E. coli. Under optimized conditions, a solution of 100 mg prochiral 2-methylmaleimide was reduced to optically pure 2-methylsuccinimide (99 % ee, 80 % yield of isolated product). High product yields and excellent optical purities demonstrate the synthetic usefulness of light-catalyzed whole-cell biotransformations using recombinant cyanobacteria.

The combination of enzymes with traditional chemical catalysts unifies the high selectivity of the former with the versatility of the latter. A major challenge of this approach is the difference in the optimal reaction conditions for each catalyst type. In this work, we combined a cofactor-free decarboxylase with a ruthenium metathesis catalyst to produce high-value antioxidants from bio-based precursors. As suitable ruthenium catalysts did not show satisfactory activity under aqueous conditions, the reaction required the use of an organic solvent, which in turn significantly reduced enzyme activity. Upon encapsulation of the decarboxylase in a cryogel, the decarboxylation could be conducted in an organic solvent, and the recovery of the enzyme after the reaction was facilitated. After an intermediate drying step, the subsequent metathesis in pure organic solvent proved to be straightforward. The synthetic utility of the cascade was demonstrated by the synthesis of the antioxidant 4,4′-dihydroxystilbene in an overall yield of 90 %.

In the search for novel platinum-based anticancer therapeutic agents, we have recently established a structural motif of (O,S) bidentate ligands bound to a Pt(II) metal center which is effective against various cancer cell lines. Aiming at further enhancing the cytotoxicity of metal-based drugs, the identification of potential biological targets and elucidation of the mode of action of selected lead compounds is of utmost importance. Here we report our studies on the DNA interaction of three representative Pt(II) complexes of the investigated series, using various model systems and analytical techniques. In detail, CD spectroscopy as well as ESI-MS and MS2 techniques were applied to gain an overall picture of the binding properties of this class of (O,S) bidentate Pt(II) compounds with defined oligonucleotide sequences in single strand, duplex or G-quadruplex form, as well as with the nucleobase 9-methylguanine. On the whole, it was demonstrated that the tested compounds interact with DNA and produce conformational changes of different extents depending on the sequence and structure of the examined oligonucleotide. Guanine was established as the preferential target within the DNA sequence, but in the absence or unavailability of guanines, alternative binding sites can be addressed. The implications of these results are thoroughly discussed.

We recently characterized a series of novel platinum(II) compounds bearing a conserved O,S binding moiety as a bifunctional ligand and evaluated their solution behavior and antiproliferative properties in vitro against a representative cancer cell line. On the whole, those platinum compounds showed an appreciable stability in mixed dimethyl sulfoxide-aqueous buffers and promising in vitro cytotoxic effects; yet they manifested a rather limited solubility in aqueous media making them poorly suitable for further pharmaceutical development. To overcome this drawback, four new derivatives of this series were prepared and characterized based on a careful choice of substituents on the O,S bidentate ligand. The solubility and stability profile of these novel compounds in a reference buffer was determined, as well as the ligands' log P(o/w) value (P(o/w) = n-octanol-water partition coefficient) as an indirect measure for the complexes' lipophilicity. The antiproliferative properties were comparatively evaluated in a panel of three cancer cell lines. The protein binding properties of the four platinum compounds were assessed using the model protein hen egg white lysozyme (HEWL), and the molecular structures of two relevant HEWL-metallodrug adducts were solved. Overall, it is shown that a proper choice of the substituents leads to a higher solubility and enables a selective fine-tuning of the antiproliferative properties. The implications of these results are thoroughly discussed.

Photosynthetic water-splitting is a powerful force to drive selective redox reactions. The need of highly expensive redox partners such as NADPH and their regeneration is one of the main bottlenecks for the application of biocatalysis at an industrial scale. Recently, the possibility of using the photosystem of cyanobacteria to supply high amounts of reduced nicotinamide to a recombinant enoate reductase opened a new strategy for overcoming this hurdle. This paper presents the expansion of the photosynthetic regeneration system to a Baeyer–Villiger monooxygenase. Despite the potential of this strategy, this work also presents some of the encountered challenges as well as possible solutions, which will require further investigation. The successful enzymatic oxygenation shows that cyanobacterial whole-cell biocatalysis is an applicable approach that allows fuelling selective oxyfunctionalisation reactions at the expense of light and water. Yet, several hurdles such as side-reactions and the cell-density limitation, probably due to self-shading of the cells, will have to be overcome on the way to synthetic applications.

Cisplatin and its analogues are first-line chemotherapeutic agents for the treatment of numerous human cancers. A major inconvenience in their clinical use is their strong tendency to link to sulfur compounds, especially in kidney, ultimately leading to severe nephrotoxicity. To overcome this drawback we prepared a variety of platinum complexes with sulfur ligands and analyzed their biological profiles. Here, a series of six platinum(II) compounds bearing a conserved O,S binding moiety have been synthesized and characterized as experimental anticancer agents. The six compounds differ in the nature of the O,S bidentate β-hydroxydithiocinnamic alkyl ester ligand where both the substituents on the aromatic ring and the length of the alkyl chain may be varied. The two remaining coordination positions at the square-planar platinum(II) center are occupied by a chloride ion and a DMSO molecule. These novel platinum compounds showed an acceptable solubility profile in mixed DMSO-buffer solutions and an appreciable stability at physiological pH as judged from analysis of their time-course UV-visible absorption spectra. Their anti-proliferative and pro-apoptotic activities were tested against the cisplatin-resistant lung cancer cell line A549. Assays revealed significant effects of the sample drugs at low concentrations (in the μmolar range); initial structure-activity-relationships are proposed. The activity of the apoptosis-promoting protein caspase 3/7 was determined; results proved that these novel platinum compounds, under the chosen experimental conditions, preferentially induce apoptosis over necrosis. Reactions with the model proteins cytochrome c, lysozyme and albumin were studied by ESI MS and ICP-OES to gain preliminary mechanistic information. The tested compounds turned out to metalate the mentioned proteins to a large extent. In view of the obtained results these novel platinum complexes qualify themselves as promising cytotoxic agents and merit, in our opinion, a deeper pharmacological evaluation as prospective anticancer agents.

Reactions of cytotoxic platinum drugs with proteins are attracting growing attention for their relevant biological implications. We report here on the reactions of two cis-diphosphane platinum(II) dichlorides (namely cis-bis(trimethylphosphane) platinum(II) dichloride and cis-bis(triethylphosphane) platinum(II) dichloride) with horse heart cytochrome c (cyt c) monitored through advanced ESI MS methods coupled to enzymatic digestion. A remarkable selectivity in terms of adduct stoichiometry is highlighted and the specific metal binding sites are localised on the protein surface.

Optically pure hydroxy amino acids show several bioactivities and are valuable building blocks for the pharmaceutical industry. Fe(II)/α-ketoglutarate dependent dioxygenases catalyze the hydroxylation or sulfoxidation of l-amino acids with high regio- and stereoselectivity. While several β- and γ-specific enzymes have been described, only one δ-specific hydroxylase has been reported so far. Based on its similarity to the known l-leucine 5-hydroxylase from Nostoc punctiforme, an open reading frame from the cyanobacterium Anabaena variabilis was identified as putative l-leucine dioxygenase (AvLDO). Here we report the cloning and characterization of this dioxygenase. The enzyme showed a high preference for acidic conditions and moderate reaction temperatures. AvLDO catalyzed the regio- and stereoselective hydroxylation of several aliphatic amino acids in δ-position. In case of the sulfoxidation of l-methionine, AvLDO produced the opposite diastereomer than isoleucine dioxygenase. AvLDO is thus an interesting addition to the toolbox of Fe(II)/α-ketoglutarate dependent dioxygenases. On the genomic DNA of Anabaena variabilis ATCC 29413, the avldo gene is located on a gene cluster involved (2S,4S)-4-methylproline biosynthesis, which is contained in bioactive peptides often found from cyanobacteria. This fact suggests the metabolic functional role of this amino acid dioxygenase in cyanobacteria.

Twelve Pt(II) complexes with cis-PtP(2)S(2) pharmacophores (where P(2) refers to two monodentate or one bidentate phosphane ligand and S(2) is a dithiolato ligand) were prepared, characterized and evaluated as potential antiproliferative agents. The various compounds were first studied from the structural point of view; afterward, their solubility properties as well as their solution behaviour were analyzed in detail. Antiproliferative properties were specifically evaluated against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin. For comparison purposes similar studies were carried out on four parent cis-dichloro bisphosphane Pt(II)complexes. On the whole, the cis-PtP(2)S(2) compounds displayed significant antiproliferative properties while the cis-PtP(2)Cl(2) (cis-dichloro bisphosphane Pt(II)) compounds revealed quite poor biological performances. To gain further insight into the molecular mechanisms of these bisphosphane Pt(II) compounds, the reactions of selected complexes against the model protein cytochrome c were investigated by ESI-MS and their adduct formation explored. A relevant reactivity with cyt c was obtained only for cis-PtP(2)Cl(2) compounds, whereas cis-PtP(2)S(2) compounds turned out to be nearly unreactive. The obtained results are interpreted and discussed in the frame of the current knowledge of anticancer platinum compounds and their structure-activity-relationships. The observation of appreciable antiproliferative effects for the relatively inert cis-PtP(2)S(2) compounds strongly suggests that these compounds will undergo specific activation within the cellular environment.