Cláudia Neves

Mimicking P 450 processes and the use of metalloporphyrins

Metalloporphyrins (MPs) are known to catalyze in vitro a broad range of cytochrome P450-mediated reactions occurring in vivo. Most of the biomimetic research using MPs in oxidative catalysis has been directed towards the oxidation of organic compounds presenting significant reactivity features in one functional group. Much less effort has been made to imitate the oxidation of more complex molecules, with a range of functionalities, such as drugs or other xenobiotics. By varying the structure of the porphyrin, the metal ion, the oxidant, and the reaction conditions, it is possible to modulate the regioselectivity of the oxidation reactions. Recently, and along with studies on the synthesis and reactivity of porphyrins, chlorins, and phthalocyanines, our group was able to develop an interesting line of research in the field of biomimetic oxidation of organic compounds using environmentally benign hydrogen peroxide as oxidant and Mn(III) or Fe(III) porphyrin complexes as catalysts. The more up to date results obtained in such work are reviewed here.

Immobilized Lignin Peroxidase-Like Metalloporphyrins as Reusable Catalysts in Oxidative Bleaching of Industrial Dyes.

Synthetic and bioinspired metalloporphyrins are a class of redox-active catalysts able to emulate several enzymes such as cytochromes P450, ligninolytic peroxidases, and peroxygenases. Their ability to perform oxidation and degradation of recalcitrant compounds, including aliphatic hydrocarbons, phenolic and non-phenolic aromatic compounds, sulfides, and nitroso-compounds, has been deeply investigated. Such a broad substrate specificity has suggested their use also in the bleaching of textile plant wastewaters. In fact, industrial dyes belong to very different chemical classes, being their effective and inexpensive oxidation an important challenge from both economic and environmental perspective. Accordingly, we review here the most widespread synthetic metalloporphyrins, and the most promising formulations for large-scale applications. In particular, we focus on the most convenient approaches for immobilization to conceive economical affordable processes. Then, the molecular routes of catalysis and the reported substrate specificity on the treatment of the most diffused textile dyes are encompassed, including the use of redox mediators and the comparison with the most common biological and enzymatic alternative, in order to depict an updated picture of a very promising field for large-scale applications.

Oxidation of diclofenac catalyzed by manganese porphyrins: synthesis of novel diclofenac derivatives

The oxidation of drugs using metalloporphyrins has been the subject of several studies in recent years. Diclofenac, one of the most frequently used anti-inflammatory drugs, is metabolized in humans by cytochrome P450 (CYP) enzymes to hydroxy-derivatives and to some metabolites resulting from oxidative decarboxylation. In this paper, the in vitro formation of several new diclofenac derivatives, initially resulting from oxidative decarboxylation, similar to what happens in vivo, is revealed. Chloro [5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinato]manganese(III), [Mn(TDCPP)Cl], and chloro [5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato]manganese(III), [Mn(TPFPP)Cl], are tested in the presence of hydrogen peroxide at room temperature. The new products obtained are fully characterized, three of them being characterized in the solid state using X-ray diffraction studies.

On tail trend detection: modeling relative risk

The climate change dispute is about changes over time of environmental characteristics (such as rainfall). Some people say that a possible change is not so much in the mean but rather in the extreme phenomena (that is, the average rainfall may not change much but heavy storms may become more or less frequent). The paper studies changes over time in the probability that some high threshold is exceeded. The model is such that the threshold does not need to be specified, the results hold for any high threshold. For simplicity a certain linear trend is studied depending on one real parameter. Estimation and testing procedures (is there a trend?) are developed. Simulation results are presented. The method is applied to trends in heavy rainfall at 18 gauging stations across Germany and The Netherlands. A tentative conclusion is that the trend seems to depend on whether or not a station is close to the sea.

Estimation of the finite right endpoint in the Gumbel domain

A simple estimator for the finite right endpoint of a distribution function in the Gumbel max-domain of attraction is proposed. Large sample properties such as consistency and the asymptotic distribution are derived. A simulation study is presented.

Ratio of Maximum to the Sum for Testing Super Heavy Tails

An extreme value approach to the modeling of rare and damaging events quite frequently involves heavy tailed distributions associated with power decaying tails. The positive counterpart of this power, which determines the tail heaviness of the distribution function pertaining to the sample observations, is consensually known as the tail index. In this paper, we allow the tail index

How Far Can Man Go

α

A general estimator for the right endpoint with an application to supercentenarian women’s records

to be zero so as to embrace the class of super-heavy tailed distributions. We then present a test statistic consisting of the ratio of maximum to the sum of log-excesses in order to discern between distributions with heavy and super-heavy tails. Under suitable yet reasonable assumptions, we cast an account of consistency of the Hill estimator for α equal to zero from the asymptotic features of the referred testing procedure.

Biomimetic oxidation of carbamazepine with hydrogen peroxide catalyzed by a manganese porphyrin

In this chapter we address the question of “What is the Largest Jump at Man’s reach, given today’s state of the art?” To answer that question it will be used the best from the best, i.e., the data will be collected from the best “jumpers” from World Athletics Competitions—“Long Jump Men Outdoors” event. Our approach to the problem is based on the probability theory of extreme values (EVT) and the corresponding statistical techniques. We shall only use the top performances of World top lists. Our estimated ultimate record, i.e., the right endpoint of the jumping event, tells us what is possible to infer about the possible personal best mark, given today’s knowledge, sports conditions and rules.

2-Amino-6-[(2,6-dichloro-phen-yl)imino]-3-oxocyclo-hexa-1,4-dienecarbaldehyde.

We extend the setting of the right endpoint estimator introduced in Fraga Alves and Neves (Statist. Sinica 24, 1811–1835, 2014) to the broader class of light-tailed distributions with finite endpoint, belonging to some domain of attraction induced by the extreme value theorem. This stretch enables a general estimator for the finite endpoint, which does not require estimation of the (supposedly non-positive) extreme value index. A new testing procedure for selecting max-domains of attraction also arises in connection with the asymptotic properties of the general endpoint estimator. The simulation study conveys that the general endpoint estimator is a valuable complement to the most usual endpoint estimators, particularly when the true extreme value index stays above −1/2, embracing the most common cases in practical applications. An illustration is provided via an extreme value analysis of supercentenarian women data.