Assembling a xylanase-lichenase chimera through all-atom molecular dynamics simulations

Multifunctional enzyme engineering can improve enzyme cocktails for emerging biofuel technology. Molecular dynamics through structure-based models (SB) is an effective tool for assessing the tridimensional arrangement of chimeric enzymes as well as for inferring the functional practicability before experimental validation. This study describes the computational design of a bifunctional xylanase-lichenase chimera (XylLich) using the xynA and bglS genes from Bacillus subtilis. In silico analysis of the average solvent accessible surface area (SAS) and the root mean square fluctuation (RMSF) predicted a fully functional chimera, with minor fluctuations and variations along the polypeptide chains. Afterwards, the chimeric enzyme was built by fusing the xynA and bglS genes. XylLich was evaluated through small-angle X-ray scattering (SAXS) experiments, resulting in scattering curves with a very accurate fit to the theoretical protein model. The chimera preserved the biochemical characteristics of the parental enzymes, with the exception of a slight variation in the temperature of operation and the catalytic efficiency (k cat/Km). The absence of substantial shifts in the catalytic mode of operation was also verified. Furthermore, the production of chimeric enzymes could be more profitable than producing a single enzyme separately, based on comparing the recombinant protein production yield and the hydrolytic activity achieved for XylLich with that of the parental enzymes. © 2013 Elsevier B.V. All rights reserved.

Estudo da preparação de nanocompósitos magneto-luminescentes unidimensionais baseados em telúrio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Inibição da atividade da Tirosinase por análogos do ácido Kójico

A tirosinase é uma enzima chave para a biossíntese de melanina. É uma enzima “cobre-dependente” que pode existir em três estados intermediários: desoxi (Cu¹⁺ -Cu¹⁺), oxi (Cu ²⁺ - O² -Cu²⁺) e met (Cu²⁺) - Cu²⁺). Apresenta atividade bifuncional, pois oxida fenóis ou catecóis em seus o-difenóis correspondentes, sendo que o processo de oxidação de fenóis pode ser descrito por cinética de Michaelis-Menten. Distúrbios na tirosinase estão associados com hiperpigmentação e escurecimento enzimático de frutas e fungos. Assim a busca por substâncias de origem natural ou sintética capazes de regular o comportamento desta enzima é fator chave para o tratamento de tais desordens. Nesta perspectiva, no presente trabalho buscou-se analisar bioquimicamente a atividade anti-tirosinase de análogos do ácido kójico derivados de 4H- pironas (S-01, S-02, S-03 e S-04) e derivados de diidropirano [3, 2-b] cromenodionas (S-05, S-06, S-07 e S-08), quimicamente planejadas por modelagem molecular no LPDF, do ICEN da UFPA. A cinética das substâncias S-02, S-04, S-06, S-07 e S-08 apresentaram inibição do tipo competitiva, semelhante ao padrão de inibição do ácido kójico, com valores de Ki de 145,0 ± 20,0 μM; 64,0 ± 10,0 μM; 4,0 ± 0,0 μM; 6,0 ± 0,0 μM; 9,0 ± 0,0 μM, respectivamente, e de 5,0 ± 0,0 μM para o ácido kójico, enquanto a substância S-01 apresentou uma inibição do tipo mista (Ki = 999,0 ± 150,0 μM). Já as substâncias S-03 e S-05 não apresentaram atividade inibitória. As substâncias testadas demonstraram alto grau de segurança tanto na integridade de membrana de eritrócitos em teste de hemólise, quanto na viabilidade em teste com MTT em culturas de fibroblasto MRC5, em cultura de células nervosas de retina de embrião de galinha e em melanoma B16F10. Assim, demonstrou-se que as substâncias S-02, S-04, S-06, S-07 e S-08 apresentam atividade como potentes inibidores de tirosinase, podendo ser candidatos no tratamento de desordens de pigmentação.

Structural characterization of diastereoisomeric ethano adducts derived from the reaction of 2'-deoxyguanosine with trans,trans-2,4-decadienal

Background levels of exocyclic DNA adducts have been detected in rodent and human tissues. Several studies have focused on bifunctional electrophiles generated from lipid peroxidation as one of the endogenous sources of these lesions. We have previously shown that the reaction of 2'-deoxyguanosine (dGuo) with trans,trans-2,4-decadienal (DDE), a highly cytotoxic aldehyde generated as a product of lipid peroxidation in cell membranes, results in the formation of a number of different base derivatives. Three of these derivatives have been fully characterized as 1,N-2-etheno-2'-deoxyguanosine adducts. In the present work, four additional adducts, designated A3-A6, were isolated from in vitro reactions by reversed-phase HPLC and fully characterized on the basis of spectroscopic measurements. Adducts A3-A6 are four diastereoisomeric 1,N-2-hydroxyethano-2'-deoxyguanosine derivatives possessing a carbon side chain with a double bond and a hydroxyl group. The systematic name of these adducts is 6-hydroxy3-(2'-deoxy-beta-D-erythro-pentafuranosyl)-7-((E)-1-hydroxy-oct-2-enyl)-3,5,6,7-tetrahydro-imidazo- [1,2-a]purin-9-one. The proposed reaction mechanism yielding adducts A3-A6 involves DDE epoxidation at C2, followed by nucleophilic addition of the exocyclic amino group of dGuo to the C1 of the aldehyde and cyclization, via nucleophilic attack, on the C2 epoxy group by N-1. The formation of adducts A1-A6 has been investigated in acidic, neutral, and basic pH in the presence of H2O2 or tent-butyl hydroperoxide. Neutral conditions, in the presence of H2O2, have favored the formation of adducts A1 and A2, with minor amounts of A3-A6, which were prevalent under basic conditions. These data indicate that DDE can modify DNA bases through different oxidative pathways involving its two double bonds. It is important to structurally characterize DNA base derivatives induced by alpha,beta-unsaturated aldehydes so that the genotoxic risks associated with the lipid peroxidation process can be assessed.

One-step glycerol oxidehydration to acrylic acid on multifunctional zeolite catalysts

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

O desenvolvimento de nanopartículas de intermetálicos ordenados de ouro e estudo da atividade eletroquímica da reação de oxidação do glicerol

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Investigation of a Pt3Sn/C Electro-Catalyst in a Direct Ethanol Fuel Cell Operating at Low Temperatures for Portable Applications

A 20% Pt3Sn/C catalyst was prepared by reduction with formic acid and used in a direct ethanol fuel cell at low temperatures. The electro-catalytic activity of this bimetallic catalyst was compared to that of a commercial 20% Pt/C catalyst. The PtSn catalyst showed better results in the investigated temperature range (30 degrees-70 degrees C). Generally, Sn promotes ethanol oxidation by adsorption of OH species at considerably lower potentials compared to Pt, allowing the occurrence of a bifunctional mechanism. The bimetallic catalyst was physico-chemically characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The presence of SnO2 in the bulk and surface of the catalyst was observed. It appears that SnO2 can enhance the ethanol electro-oxidation activity at low potentials due to the supply of oxygen-containing species for the oxidative removal of CO and CH3CO species adsorbed on adjacent Pt active sites.

PtSnIr/C Anode Electrocatalysts: Promoting Effect in Direct Ethanol Fuel Cells

This study investigates the promoting effect of PtSnIr/C (1:1:1) electrocatalyst anode, prepared by polymeric precursor method, on the ethanol oxidation reaction in a direct ethanol fuel cell (DEFC). All of the materials used were 20% metal m/m on carbon. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Pt, PtOH2, PtO2, SnO2 and IrO2 at the electrocatalyst surface, indicating a possible decorated particle structure. X-ray diffractometry (XRD) analysis indicated metallic Pt and Ir as well as the formation of an alloy with Sn. Using the PtSnIr/C electrocatalyst prepared here with two times lower loading of Pt than PtSn/C E-tek electrocatalyst, it was possible to obtain the same maximum power density found for the commercial material. The main reaction product was acetic acid probably due to the presence of oxides, in this point the bifunctional mechanism is predominant, but an electronic effect should not be discarded.

PtSnIr/C anode electrocatalysts: promoting effect in direct ethanol fuel cells

This study investigates the promoting effect of PtSnIr/C (1:1:1) electrocatalyst anode, prepared by polymeric precursor method, on the ethanol oxidation reaction in a direct ethanol fuel cell (DEFC). All of the materials used were 20% metal m/m on carbon. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Pt, PtOH2, PtO2, SnO2 and IrO2 at the electrocatalyst surface, indicating a possible decorated particle structure. X-ray diffractometry (XRD) analysis indicated metallic Pt and Ir as well as the formation of an alloy with Sn. Using the PtSnIr/C electrocatalyst prepared here with two times lower loading of Pt than PtSn/C E-tek electrocatalyst, it was possible to obtain the same maximum power density found for the commercial material. The main reaction product was acetic acid probably due to the presence of oxides, in this point the bifunctional mechanism is predominant, but an electronic effect should not be discarded.

Synthese und Charakterisierung von Poly(tert-butylacrylat)- und Polyacrylsäure-Sternpolymeren

Sternpolymere aus Poly(tert.-butylacrylat)-Armen und einem Mikrogel-Core aus Ethylenglykoldimethacrylat wurden nach der arm-first Strategie hergestellt. Diese weisen eine enge Armzahlverteilung auf. Mit sinkender Precursorlänge, mit steigendem Verhältnis [bifunktionelles Monomer]/[Initiator], sowie mit zunehmender Reaktionszeit und Gesamtkonzentration nimmt die mittlere Armzahl fn zu. Die Sternbildung verläuft ähnlich einer Polykondensation. Die Molekulargewichte wurden mittels GPC gekoppelt mit einem online-Viskosimeter und einem online-Vielwinkellichtstreudetektor (MALLS) bestimmt.Die intrinsischen Viskositäten der Sternpolymere sind sehr niedrig. Für Armzahlen f ca. 8 erhält man ein Maximum in der doppellogarithmischen Auftragung der intrinsischen Viskosität und des Molekulargewichts. Die Trägheitsradien nehmen nur wenig mit dem Molekulargewicht zu. Die erhaltenen Koeffizienten liegen im von Daoud und Cotton vorhergesagten Bereich. Die Schrumpfungsfaktoren sinken auf g ca. 0,2 bzw. g' ca. 0,25. Aus den Poly(tert.-butylacrylat)-Sternpolymeren wurden durch Verseifung mit HBr in Methanol Polyacrylsäure-Sternpolymere hergestellt, welche ebenfalls mittels GPC-Viskosimetrie und GPC-MALLS charakterisiert wurden. Für die ionischen Sternpolymere findet man deutlich höhere Schrumpfungsfaktoren, kein Maximum in der intrinsischen Viskosität und höhere Exponenten als von Daoud und Cotton vorhergesagt. Erklärt wurde dies mit der hohen Segmentdichte in Sternpolymeren, die bei den ionischen Sternpolymeren zu einer hohen Ladungsdichte führt. Dadurch müssen sich die Arme stärker strecken als bei nicht-ionischen Sternen und es resultieren größere Moleküldimensionen.

Catalytic liquid- and gas-phase oxidations for the synthesis of intermediates and specialty chemicals: some examples of industrial relevance

Nowadays, it is clear that the target of creating a sustainable future for the next generations requires to re-think the industrial application of chemistry. It is also evident that more sustainable chemical processes may be economically convenient, in comparison with the conventional ones, because fewer by-products means lower costs for raw materials, for separation and for disposal treatments; but also it implies an increase of productivity and, as a consequence, smaller reactors can be used. In addition, an indirect gain could derive from the better public image of the company, marketing sustainable products or processes. In this context, oxidation reactions play a major role, being the tool for the production of huge quantities of chemical intermediates and specialties. Potentially, the impact of these productions on the environment could have been much worse than it is, if a continuous efforts hadn’t been spent to improve the technologies employed. Substantial technological innovations have driven the development of new catalytic systems, the improvement of reactions and process technologies, contributing to move the chemical industry in the direction of a more sustainable and ecological approach. The roadmap for the application of these concepts includes new synthetic strategies, alternative reactants, catalysts heterogenisation and innovative reactor configurations and process design. Actually, in order to implement all these ideas into real projects, the development of more efficient reactions is one primary target. Yield, selectivity and space-time yield are the right metrics for evaluating the reaction efficiency. In the case of catalytic selective oxidation, the control of selectivity has always been the principal issue, because the formation of total oxidation products (carbon oxides) is thermodynamically more favoured than the formation of the desired, partially oxidized compound. As a matter of fact, only in few oxidation reactions a total, or close to total, conversion is achieved, and usually the selectivity is limited by the formation of by-products or co-products, that often implies unfavourable process economics; moreover, sometimes the cost of the oxidant further penalizes the process. During my PhD work, I have investigated four reactions that are emblematic of the new approaches used in the chemical industry. In the Part A of my thesis, a new process aimed at a more sustainable production of menadione (vitamin K3) is described. The “greener” approach includes the use of hydrogen peroxide in place of chromate (from a stoichiometric oxidation to a catalytic oxidation), also avoiding the production of dangerous waste. Moreover, I have studied the possibility of using an heterogeneous catalytic system, able to efficiently activate hydrogen peroxide. Indeed, the overall process would be carried out in two different steps: the first is the methylation of 1-naphthol with methanol to yield 2-methyl-1-naphthol, the second one is the oxidation of the latter compound to menadione. The catalyst for this latter step, the reaction object of my investigation, consists of Nb2O5-SiO2 prepared with the sol-gel technique. The catalytic tests were first carried out under conditions that simulate the in-situ generation of hydrogen peroxide, that means using a low concentration of the oxidant. Then, experiments were carried out using higher hydrogen peroxide concentration. The study of the reaction mechanism was fundamental to get indications about the best operative conditions, and improve the selectivity to menadione. In the Part B, I explored the direct oxidation of benzene to phenol with hydrogen peroxide. The industrial process for phenol is the oxidation of cumene with oxygen, that also co-produces acetone. This can be considered a case of how economics could drive the sustainability issue; in fact, the new process allowing to obtain directly phenol, besides avoiding the co-production of acetone (a burden for phenol, because the market requirements for the two products are quite different), might be economically convenient with respect to the conventional process, if a high selectivity to phenol were obtained. Titanium silicalite-1 (TS-1) is the catalyst chosen for this reaction. Comparing the reactivity results obtained with some TS-1 samples having different chemical-physical properties, and analyzing in detail the effect of the more important reaction parameters, we could formulate some hypothesis concerning the reaction network and mechanism. Part C of my thesis deals with the hydroxylation of phenol to hydroquinone and catechol. This reaction is already industrially applied but, for economical reason, an improvement of the selectivity to the para di-hydroxilated compound and a decrease of the selectivity to the ortho isomer would be desirable. Also in this case, the catalyst used was the TS-1. The aim of my research was to find out a method to control the selectivity ratio between the two isomers, and finally to make the industrial process more flexible, in order to adapt the process performance in function of fluctuations of the market requirements. The reaction was carried out in both a batch stirred reactor and in a re-circulating fixed-bed reactor. In the first system, the effect of various reaction parameters on catalytic behaviour was investigated: type of solvent or co-solvent, and particle size. With the second reactor type, I investigated the possibility to use a continuous system, and the catalyst shaped in extrudates (instead of powder), in order to avoid the catalyst filtration step. Finally, part D deals with the study of a new process for the valorisation of glycerol, by means of transformation into valuable chemicals. This molecule is nowadays produced in big amount, being a co-product in biodiesel synthesis; therefore, it is considered a raw material from renewable resources (a bio-platform molecule). Initially, we tested the oxidation of glycerol in the liquid-phase, with hydrogen peroxide and TS-1. However, results achieved were not satisfactory. Then we investigated the gas-phase transformation of glycerol into acrylic acid, with the intermediate formation of acrolein; the latter can be obtained by dehydration of glycerol, and then can be oxidized into acrylic acid. Actually, the oxidation step from acrolein to acrylic acid is already optimized at an industrial level; therefore, we decided to investigate in depth the first step of the process. I studied the reactivity of heterogeneous acid catalysts based on sulphated zirconia. Tests were carried out both in aerobic and anaerobic conditions, in order to investigate the effect of oxygen on the catalyst deactivation rate (one main problem usually met in glycerol dehydration). Finally, I studied the reactivity of bifunctional systems, made of Keggin-type polyoxometalates, either alone or supported over sulphated zirconia, in this way combining the acid functionality (necessary for the dehydrative step) with the redox one (necessary for the oxidative step). In conclusion, during my PhD work I investigated reactions that apply the “green chemistry” rules and strategies; in particular, I studied new greener approaches for the synthesis of chemicals (Part A and Part B), the optimisation of reaction parameters to make the oxidation process more flexible (Part C), and the use of a bioplatform molecule for the synthesis of a chemical intermediate (Part D).

Formtreue organische Makrocyclen mit polarem Innenraum

Zusammenfassung Die Arbeit beschreibt die Synthese und Eigenschaften von formtreuen organischen Makrocyclen mit intraannularen polaren Gruppen. Dabei wurden zunächst entsprechende bifunktionalisierte Acetylenbausteine (Halbringe) hergestellt, welche anschließend in einer oxidativen Glaser-Eglington Kupplung zu den Makrocyclen umgesetzt wurden.Am Anfang wurden Sulfonat-funktionalisierte Makrocyclen untersucht. Diese ließen sich mittels der Templatmethode in hohen Ausbeuten synthetisieren. Nach der Abspaltung des Templatbausteins, der gleichzeitig als Schutzgruppe für die Sulfonsäure diente, erhielt man den entsprechenden Makrocyclus als Tetra-n-butylammonium-Salz. Vor dem Hintergrund ionenleitfähige Materialien zu erhalten, wurde anschließend das organische Kation durch anorganische Kationen (z.B. Li+, Na+) ausgetauscht. Dies führte jedoch zur Bildung unlöslicher Produkte, die sich nicht eindeutig charakterisierten ließen.Ein anderer Ansatz zu löslichen Makrocyclen mit polarem Innenraum zu gelangen war die Synthese eines Dipeptid-funktionalisierten Makrocyclus. Dies geschah im Hinblick auf die eventuelle Eignung der Makrocyclen als Rezeptormoleküle für Gäste biologischen Ursprungs. Dabei ließen sich die entsprechenden Dipeptid-funktionalisierten Halbringe auf einfache Weise darstellen, jedoch trat bei der anschließenden Glaser-Kupplung, wahrscheinlich bedingt durch den hohen molaren Überschuß an Kupfersalzen, als Hauptreaktion die Abspaltung des Peptidrests auf. Daher wurde sich nun der Carbonsäuregruppe als polaren Baustein im Inneren der Ringe zugewandt. Diese sollten eine anschließende Peptidankupplung zulassen.Es wurden vier verschiedene Makrocyclen mit intraannularen Carboxylatgruppen synthetisiert. Auch hier waren die Makrocyclen in Form ihrer Methylester noch gut, in Form der Säuren oder deren Salze oftmals nur noch sehr gering löslich. Um die Löslichkeit zu verbessern, wurde dabei die Polaritätsverteilung am Ring (polarer Innenraum, unpolarer Außenraum) durch das Anbringen von löslichkeits-vermittelnden Gruppen zum Teil aufgegeben. Dabei hat sich gezeigt, daß es erst durch die Verwendung von verzweigten (S)-Methylbutoxy-Gruppen innerhalb des Rings oder langen Alkoxyketten außerhalb des Rings möglich war, zu löslichen Systemen zu gelangen. Im ersten Fall ist es zum ersten Mal gelungen, einen löslichen Makrocyclus mit zwei freien intra-annnularen Carbonsäuregruppen zu erhalten. Durch die Optimierung der Syntheseroute ist es nunmehr möglich, den Ring im Grammmaßstab herzustellen. Außerdem wurden als Testreaktion beide Säuregruppen mit Methylamin zum Säureamid vollständig umgesetzt. Somit wurde ein System entwickelt, an das sich in Zukunft beliebige Aminosäuren an den Ring anbinden lassen sollten. Zusätzlich sollte sich die Chiralität der (S)-Methylbutoxygruppen auf das Erkennen von chiralen Gästen auswirken.Im zweiten Fall wurden durch das Anbringen von vier Tris(hexadecyloxy)-benzol- oder Tris(dodecyloxy)-benzol- Gruppen an der Peripherie der Ringe nach Hydrolyse der Methylestergruppen ebenfalls lösliche, Carboxylat-funktionalisierte Makrocyclen erhalten. Eine eingehende Untersuchung der Methylester-geschützten Ringe ergab, daß diese beim Schmelzen das Auftreten einer thermotropen flüssigkristallinen Phase zeigen. Die Natur der Mesophase konnte mittels Polarisations-Lichtmikroskopie sowie Röntgenbeugungsmethoden eindeutig als kolumnar-schiefwinklig (colob) charakterisiert werden. Hierbei ist zu bemerken, daß bei ähnlichen Makrocyclen, die über keinen polar gefüllten Innenraum verfügen, keine Mesophase auftritt. Das bedeutet, daß die Raumerfüllung im Inneren der Makrocyclen, bedingt durch die polaren Gruppen, zur Ausbildung einer flüssigkristallinen Phase unbedingt notwendig ist.

Neue Katalysatoren für die asymmetrische Strecker-Reaktion auf Kohlenhydratbasis

Die asymmetrische Strecker-Reaktion ist von großer Bedeutung zur Darstellung optisch aktiver natürlicher und artifizieller -Aminocarbonsäuren beider Enantiomerenreihen. In der vorliegenden Arbeit wurden Synthesen einer Reihe von metallfreien, löslichen und immobilisierten Organokatalysatoren auf Kohlenhydratbasis für die enantioselektive Hydrocyanierung von Iminen ausgearbeitet. Durch gezielte Variation sowohl der Substituenten als auch des monosaccharidischen chiralen Rückgrates, konnten durch Aktivitäts- und Selektivitätsvergleich mit bereits bekannten Glucokatalysatoren und mit Hilfe einfacher, durch MM2-Kraftfeldmethoden gewonnener, Molekülmodelle Struktur-Wirkungs-Beziehungen aufgestellt und Rückschlüsse auf den mechanistischen Ablauf der enantioselektiven pseudo-Strecker-Reaktion gezogen werden.

Asymmetric aminocatalysis: a modern strategy for molecules, challenges and life

The studies conducted during my Phd thesis were focused on two different directions: 1. In one case we tried to face some long standing problems of the asymmetric aminocatalysis as the activation of encumbered carbonyl compounds and the control of the diastereoisomeric ratio in the diastero- and enantioselective construction of all carbon substituted quaternary stereocenters adjacent a tertiary one. In this section (Challenges) was described the asymmetric aziridination of ,-unsaturated ketones, the activation of ,-unsaturated -branched aldehydes and the Michael addition of oxindoles to enals and enones. For the activation via iminium ion formation of sterically demanding substrates, as ,-unsaturated ketones and ,-unsaturated -branched aldehydes, we exploited a chiral primary amine in order to overcome the problem of the iminium ion formation between the catalyst and encumbered carbonylic componds. For the control of diastereoisomeric ratio in the diastero- and enantioselective construction of all carbon substituted quaternary stereocenters adjacent a tertiary one we envisaged that a suitable strategy was the Michael addition to 3 substituted oxindoles to enals activated via LUMO-lowering catalysis. In this synthetic protocol we designed a new bifunctional catalyst with an amine moiety for activate the aldehyde and a tioureidic fragment for direct the approach of the oxindole. This part of the thesis (Challenges) could be considered pure basic research, where the solution of the synthetic problem was the goal itself of the research. 2. In the other hand (Molecules) we applied our knowledge about the carbonylic compounds activation and about cascade reaction to the synthesis of three new classes of spirooxindole in enantiopure form. The construction of libraries of these bioactive compounds represented a scientific bridge between medicinal chemistry or biology and the asymmetric catalysis.

Radiochemical aspects of production and processing of radiometals for preparation of metalloradiopharmaceuticals

Radiometals play an important role in nuclear medicine as involved in diagnostic or therapeutic agents. In the present work the radiochemical aspects of production and processing of very promising radiometals of the third group of the periodic table, namely radiogallium and radiolanthanides are investigated. The 68Ge/68Ga generator (68Ge, T½ = 270.8 d) provides a cyclotron-independent source of positron-emitting 68Ga (T½ = 68 min), which can be used for coordinative labelling. However, for labelling of biomolecules via bifunctional chelators, particularly if legal aspects of production of radiopharmaceuticals are considered, 68Ga(III) as eluted initially needs to be pre-concentrated and purified. The first experimental chapter describes a system for simple and efficient handling of the 68Ge/68Ga generator eluates with a cation-exchange micro-chromatography column as the main component. Chemical purification and volume concentration of 68Ga(III) are carried out in hydrochloric acid – acetone media. Finally, generator produced 68Ga(III) is obtained with an excellent radiochemical and chemical purity in a minimised volume in a form applicable directly for the synthesis of 68Ga-labelled radiopharmaceuticals. For labelling with 68Ga(III), somatostatin analogue DOTA-octreotides (DOTATOC, DOTANOC) are used. 68Ga-DOTATOC and 68Ga-DOTANOC were successfully used to diagnose human somatostatin receptor-expressing tumours with PET/CT. Additionally, the proposed method was adapted for purification and medical utilisation of the cyclotron produced SPECT gallium radionuclide 67Ga(III). Second experimental chapter discusses a diagnostic radiolanthanide 140Nd, produced by irradiation of macro amounts of natural CeO2 and Pr2O3 in natCe(3He,xn)140Nd and 141Pr(p,2n)140Nd nuclear reactions, respectively. With this produced and processed 140Nd an efficient 140Nd/140Pr radionuclide generator system has been developed and evaluated. The principle of radiochemical separation of the mother and daughter radiolanthanides is based on physical-chemical transitions (hot-atom effects) of 140Pr following the electron capture process of 140Nd. The mother radionuclide 140Nd(III) is quantitatively absorbed on a solid phase matrix in the chemical form of 140Nd-DOTA-conjugated complexes, while daughter nuclide 140Pr is generated in an ionic species. With a very high elution yield and satisfactory chemical and radiolytical stability the system could able to provide the short-lived positron-emitting radiolanthanide 140Pr for PET investigations. In the third experimental chapter, analogously to physical-chemical transitions after the radioactive decay of 140Nd in 140Pr-DOTA, the rapture of the chemical bond between a radiolanthanide and the DOTA ligand, after the thermal neutron capture reaction (Szilard-Chalmers effect) was evaluated for production of the relevant radiolanthanides with high specific activity at TRIGA II Mainz nuclear reactor. The physical-chemical model was developed and first quantitative data are presented. As an example, 166Ho could be produced with a specific activity higher than its limiting value for TRIGA II Mainz, namely about 2 GBq/mg versus 0.9 GBq/mg. While free 166Ho(III) is produced in situ, it is not forming a 166Ho-DOTA complex and therefore can be separated from the inactive 165Ho-DOTA material. The analysis of the experimental data shows that radionuclides with half-life T½ < 64 h can be produced on TRIGA II Mainz nuclear reactor, with specific activity higher than any available at irradiation of simple targets e.g. oxides.