Sementes de leguminosas forrageiras sob estresse salino tratadas com ácido salicílico e espermidina

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analytical method for determination of nitric oxide in zebrafish larvae: Toxicological and pharmacological applications

Zebrafish are currently used at various stages of the drug discovery process and can be a useful and cost-effective alternative to some mammalian models. Nitric oxide (NO) plays an important role in physiology of zebrafish. The availability of appropriate analytical techniques to quantify the NO is crucial for studying its role in physiological and pathological conditions. This work aimed at establishing a high-performance liquid chromatography method for determination of NO levels in zebrafish larvae. Attempts were also made to assess the normal levels of NO at the first days postfertilization and the possible changes under pathological conditions. The method validation was quantitatively evaluated in terms of sensitivity, specificity, precision, accuracy, linearity, and recovery. NO levels from zebrafish larvae at the first days postfertilization and larvae challenged to N(G)-nitro-L-arginine methyl ester, sodium nitroprusside, Escherichia coil lipopolysaccharide, and copper sulfate were analyzed. The samples were derivatized with 2,3-diaminonaphthalene, and fluorescence detection was used for the indirect determination of NO. The method showed a good performance for all validation parameters evaluated and was efficient to monitor changes in NO concentration under physiological and pathophysiological conditions. This method might represent a powerful tool to be applied in NO studies with zebrafish larvae. (C) 2011 Elsevier Inc. All rights reserved.

Knock out of neuronal nitric oxide synthase exacerbates intestinal ischemia/reperfusion injury in mice

Recent investigation of the intestine following ischemia and reperfusion (I/R) has revealed that nitric oxide synthase (NOS) neurons are more strongly affected than other neuron types. This implies that NO originating from NOS neurons contributes to neuronal damage. However, there is also evidence of the neuroprotective effects of NO. In this study, we compared the effects of I/R on the intestines of neuronal NOS knockout (nNOS(-/-)) mice and wild-type mice. I/R caused histological damage to the mucosa and muscle and infiltration of neutrophils into the external muscle layers. Damage to the mucosa and muscle was more severe and greater infiltration by neutrophils occurred in the first 24 h in nNOS(-/-) mice. Immunohistochemistry for the contractile protein, alpha-smooth muscle actin, was used to evaluate muscle damage. Smooth muscle actin occurred in the majority of smooth muscle cells in the external musculature of normal mice but was absent from most cells and was reduced in the cytoplasm of other cells following I/R. The loss was greater in nNOS(-/-) mice. Basal contractile activity of the longitudinal muscle and contractile responses to nerve stimulation or a muscarinic agonist were reduced in regions subjected to I/R and the effects were greater in nNOS(-/-) mice. Reductions in responsiveness also occurred in regions of operated mice not subjected to I/R. This is attributed to post-operative ileus that is not significantly affected by knockout of nNOS. The results indicate that deleterious effects are greater in regions subjected to I/R in mice lacking nNOS compared with normal mice, implying that NO produced by nNOS has protective effects that outweigh any damaging effect of this free radical produced by enteric neurons.

Erythropoietin prevents sepsis-related acute kidney injury in rats by inhibiting NF-kappa B and upregulating endothelial nitric oxide synthase

de Souza ACCP, Volpini RA, Shimizu MH, Sanches TR, Camara NOS, Semedo P, Rodrigues CE, Seguro AC, Andrade L. Erythropoietin prevents sepsis-related acute kidney injury in rats by inhibiting nuclear factor-kappa B and upregulating endothelial nitric oxide synthase. Am J Physiol Renal Physiol 302: F1045-F1054, 2012. First published January 11, 2012; doi:10.1152/ajprenal.00148.2011.-The pathophysiology of sepsis involves complex cytokine and inflammatory mediator networks, a mechanism to which NF-kappa B activation is central. Downregulation of endothelial nitric oxide synthase (eNOS) contributes to sepsis-induced endothelial dysfunction. Erythropoietin (EPO) has emerged as a major tissue-protective cytokine in the setting of stress. We investigated the role of EPO in sepsis-related acute kidney injury using a cecal ligation and puncture (CLP) model. Wistar rats were divided into three primary groups: control (sham-operated); CLP; and CLP + EPO. EPO (4,000 IU/kg body wt ip) was administered 24 and 1 h before CLP. Another group of rats received N-nitro-L-arginine methyl ester (L-NAME) simultaneously with EPO administration (CLP + EPO + L-NAME). A fifth group (CLP + EPOtreat) received EPO at 1 and 4 h after CLP. At 48 h postprocedure, CLP + EPO rats presented significantly higher inulin clearance than did CLP and CLP + EPO + L-NAME rats; hematocrit levels, mean arterial pressure, and metabolic balance remained unchanged in the CLP + EPO rats; and inulin clearance was significantly higher in CLP + EPOtreat rats than in CLP rats. At 48 h after CLP, creatinine clearance was significantly higher in the CLP + EPO rats than in the CLP rats. In renal tissue, pre-CLP EPO administration prevented the sepsis-induced increase in macrophage infiltration, as well as preserving eNOS expression, EPO receptor (EpoR) expression, IKK-alpha activation, NF-kappa B activation, and inflammatory cytokine levels, thereby increasing survival. We conclude that this protection, which appears to be dependent on EpoR activation and on eNOS expression, is attributable, in part, to inhibition of the inflammatory response via NF-kappa B downregulation.

Signaling Events During Cyclic Guanosine Monophosphate-Regulated Pigment Aggregation in Freshwater Shrimp Chromatophores

Crustacean color change results partly from granule aggregation induced by red pigment concentrating hormone (RPCH). In shrimp chromatophores, both the cyclic GMP (3', 5'-guanosine monophosphate) and Ca2+ cascades mediate pigment aggregation. However, the signaling elements upstream and downstream from cGMP synthesis by GC-S (cytosolic guanylyl cyclase) remain obscure. We investigate post-RPCH binding events in perfused red ovarian chromatophores to disclose the steps modulating cGMP concentration, which regulates granule translocation. The inhibition of calcium/calmodulin complex (Ca2+/CaM) by N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7) induces spontaneous aggregation but inhibits RPCH-triggered aggregation, suggesting a role in pigment aggregation and dispersion. Nitric oxide synthase inhibition by N omega-nitro-L-arginine methyl ester hydrochloride (L-NAME) strongly diminishes RPCH-induced aggregation; protein kinase G inhibition (by rp-cGMPs-triethylamine) reduces RPCH-triggered aggregation and provokes spontaneous dispersion, disclosing NO/PKG participation in aggregation signaling. Myosin light chain phosphatase inhibition (by cantharidin) accelerates RPCH-triggered aggregation, whereas Rho-associated protein kinase inhibition (by Y-27632, H-11522) reduces RPCH-induced aggregation and accelerates dispersion. MLCP (myosin light chain kinase) and ROCK (Rho-associated protein kinase) may antagonistically regulate myosin light chain (MLC) dephosphorylation/phosphorylation during pigment dispersion/aggregation. We propose the following general hypothesis for the cGMP/Ca2+ cascades that regulate pigment aggregation in crustacean chromatophores: RPCH binding increases Ca2+ (int), activating the Ca2+/CaM complex, releasing NOS-produced nitric oxide, and causing GC-S to synthesize cGMP that activates PKG, which phosphorylates an MLC activation site. Myosin motor activity is initiated by phosphorylation of an MLC regulatory site by ROCK activity and terminated by MLCP-mediated dephosphorylation. Qualitative comparison reveals that this signaling pathway is conserved in vertebrate and invertebrate chromatophores alike.

Long-lasting Hypotensive Effect in Renal Hypertensive Rats Induced by Nitric Oxide Released From a Ruthenium Complex

In this study, we investigated the effect of the ruthenium complex [Ru(terpy)(bdq)NO+](3+) (TERPY) on the arterial pressure from renal hypertensive 2 kidney-1 clip (2K-1C) rats, which was compared with sodium nitroprusside (SNP). The most interesting finding was that the intravenous bolus injection of TERPY (2.5, 5.0, 7 mg/kg) had a dose-dependent hypotensive effect only in 2K-1C rats. On the other hand, SNP (35 and 70 mu g/kg) presented a similar hypotensive effect in both normotensive (2K) and 2K-1C although the effect of 70 mu g/kg was >35 mu g/kg. The injection of the nonselective NO-synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME) increased the arterial pressure in 2K and 2K-1C rats with a similar magnitude. After infusion of L-NAME, the hypotensive effect induced by TERPY and SNP was potentiated in both 2K and in 2K-1C rats. The administration of the superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl increased the hypotensive effect induced by TERPY or SNP in both 2K and 2K-1C rats. The hypotensive effect induced by TERPY was longer than that produced by SNP. Taken together, our results show that the TERPY has a long-lasting hypotensive effect, which has a dose dependence and higher magnitude in 2K-1C compared with in 2K rats. In comparison with SNP, TERPY is less potent in inducing arterial pressure fall, but it presents a much longer hypotensive effect.

Effect of fungicides and alternative products in control of anthracnose and black spot of guava

This work aimed to evaluate the efficiency of fungicides in controlling in vitro and in vivo the causal agents of anthracnose (Colletotrichum gloeosporioides and C. acutatum) and black spot (Guignardia psidii) and evaluate the effect of alternative products to control these diseases. Inhibition of mycelial growth of the pathogens was evaluated for ten fungicides at concentrations of 1, 10 and 100 mg L-1 of active ingredient in potato-dextrose-agar medium. The effectiveness of the fungicides azoxystrobin + difenoconazole, cyproconazole, pyraclostrobin, tebuconazole and tebuconazole + trifloxystrobin in controlling disease incidence and severity of anthracnose, through applications in the field, was measured in fruits collected at three stages of maturation, according to the skin color ( dark green, light green and yellowish green). In postharvest dipping of fruits, the products evaluated were citric acid, peracetic acid, salicylic acid, sodium bicarbonate, chlorine dioxide, Ecolife (R) and chitosan. The fungicides azoxystrobin + difenoconazole, pyraclostrobin, tebuconazole and trifloxystrobin + tebuconazole were highly effective in inhibiting the in vitro mycelial growth of G. psidii and moderately to highly effective in inhibiting C. acutatum and C. gloeosporioides. In field conditions, the fungicide azoxystrobin + difenoconazole was effective in controlling anthracnose and black spot in fruit at three maturity stage ( skin color yellowish green). The alternative products tested were ineffective in the curative control of anthracnose and early blight at postharvest of guava.

Pain in photodynamic therapy: mechanism of action and management strategies

Photodynamic therapy involves administration of a photosensitizing drug and its subsequent activation by irradiation with a light source at wavelengths matching the absorption spectrum of the photosensitizer. In many countries around the world, topical photodynamic therapy has been approved for treatment of cutaneous oncologic conditions such as actinic keratosis, Bowen's disease, and superficial basal cell carcinoma. Multicenter, randomized, controlled studies have confirmed its efficacy and superior cosmetic outcomes compared to conventional therapies. Nevertheless, this therapeutic method presents some adverse effects, such as erythema, edema, pigmentation, pustules, and pain. There is no doubt that pain is the most severe of the adverse effects, being sometimes responsible for definitive treatment interruption. The pain mechanism has not yet been fully understood, which makes complete pain control a challenge to be conquered. In spite of that, this literature review presents some useful pain management strategies as well as the most important pain-related factors in photodynamic therapy.

Asymmetric synthesis of benzylic and heterobenzylic amines

C2-Symmetrical, enantiopure 2,6-di[1-(1-aziridinyl)alkyl]pyridines (DIAZAPs) were prepared by a high-yielding, three-step sequence starting from 2,6-pyridinedicarbaldehyde and (S)-valinol or (S)-phenylglycinol. The new compounds were tested as ligands in palladium-catalyzed allylation of carbanions in different solvents. Almost quantitative yield and up to 99% enantiomeric excess were obtained in the reactions of the enolates derived from malonate, phenyl- and benzylmalonate dimethyl esters with 1,3-diphenyl-2-propenyl ethyl carbonate. Asymmetric synthesis of 2-(2-pyridyl)aziridines from chiral 2-pyridineimines bearing a stereogenic center at the nitrogen atom was development. The envisioned route involves the addition of chloromethyllithium to the imine derived from 2-pyridinealdehyde and (S)-valinol, protected as O-trimethylsilyl ether. The analogous reaction performed on the imine derived from (S)-valine methyl ester gave the product containing the aziridine ring as well as the α-chloro ketone group coming from the attack of chloromethyllithium to the ester function. Other stereogenic alkyl substituents at nitrogen gave less satisfactory results. Moreover, the aziridination protocol did not work on other aromatic imines, e.g. 3-pyridineimine and benzaldimine, which are not capable of bidentate chelation. The N-substituent could not be removed, but aziridine underwent ring-opening by attack of nitrogen, sulfur, and oxygen nucleophiles. Complete or prevalent regioselectivity was obtained using cerium trichloride heptahydrate as a catalyst. In some cases, the N-substituent could be removed by an oxidative protocol. The addition of organometallic (lithium, magnesium, zinc) reagents to 2-pyrroleimines derived from (S)-valinol and (S)-phenylglycinol gave the N-substituted-1-(2-pyrrolyl)alkylamines with high yields and diastereoselectivities. The (S,S)-diastereomers were useful intermediates for the preparation of enantiopure 1-[1-(2-pyrrolyl)alkyl]aziridines by routine cyclization of the β-aminoalcohol moiety and of (S)-N-benzoyl 1-[1-(2-pyrrolyl)alkyl]amines and their N-substituted derivatives by oxidative cleavage of the chiral auxiliary. 1-Allyl-2-pyrroleimines obtained from (S)-phenylglycinol and (S)-valinol underwent highly diastereoselective addition of allylmetal reagents, used in excess amounts, to give the corresponding secondary amines with concomitant allyl to 1-propenyl isomerisation of the 1-pyrrole substituent. Protection of the 2-aminoalcohol moiety as oxazolidinone, amide or Boc derivate followed by ring closing metathesis of the alkene groups gave the unsaturated bicyclic compound, whose hydrogenation afforded the indolizidine derivative as a mixture of separable diastereomers. The absolute configuration of the main diastereomer was assessed by X-ray crystallographic analysis.

Untersuchungen zur Genexpression in Wurzeln der reblausresistenten Unterlagsrebsorte ’Börner’

Die reblausresistente Unterlagsrebsorte ’Börner’ reagiert auf einen Reblausbefall mit einer Hypersensitivitätsreaktion (HR), die sich in Form von Nekrosen an Blättern und Wurzeln zeigt. Im Rahmen dieser Dissertation wurde der Resistenzmechanismus mittels differenzieller Genexpressionsanalysen untersucht. Unter Anwendung der suppressiven subtraktiven Hybridisierung, der DNA-Microarraytechnik sowie der GeneFishingTM-Methode erfolgte ein Vergleich zwischen der Genexpression in hypersensitivem Wurzelgewebe und Normalgewebe der Unterlagsrebe ’Börner’. Neben der Reblaus induzierten HR wurde insbesondere auf die experimentelle Induktion durch das Pflanzenhormon Indol-3-Essigsäure (IES) zurückgegriffen. Damit sollten Kenntnisse über die Rolle der IES als auslösender Faktor der Resistenzreaktion gewonnen werden. Die Ergebnisse bestätigen die Annahme, dass die IES Pathogenabwehrreaktionen in ’Börner’ induziert. So konnten Hinweise auf die transkriptionelle Aktivierung Resistenz und HR assoziierter Proteine gefunden werden, wie z.B. Phytoalexine und pathogen-related (PR)-Proteine sowie Vertreter aus der hypersensitive-induced response-Familie. Es konnten weiterhin wertvolle Informationen im Hinblick auf die Transduktion des IES-Signals im Zusammenhang mit der Aktivierung von Resistenzreaktionen gewonnen werden. So wurden Hinweise auf die Beteiligung der Signalsubstanzen Ethylen, Salicylsäure, Jasmonsäure, Calcium sowie reaktiver Sauerstoffspezies gefunden. Es konnten zudem Anhaltspunkte für die Aktivierung des Auxin induzierten Ubiquitin/26S-Proteolyseweges und weiterer Signalkomponenten, wie z.B. Kinasen und Transkriptionsfaktoren, ermittelt werden. Auch auf die Beteiligung von Auxinrezeptoren konnte aufgrund der Resultate geschlossen werden. Damit war es im Rahmen der Dissertation möglich, potenzielle Signaltransduktionswege zu erarbeiten, die für weiterführende Untersuchungen des Reblausresistenzmechanismus von entscheidender Bedeutung sind.

Melanocytes: a new potential tool to study and monitoring Duchenne muscular dystrophy

Dystrophin is a subsarcolemmal protein critical for the integrity of muscle fibers by linking the actin cytoskeleton to the extracellular matrix via the dystroglycan complex. It is reported that dystroglycans are also localized in the skin, at dermal-epidermal junction. Here we show that epidermal melanocytes express dystrophin at the interface with the basement membrane. The full-length muscle isoform mDp427 was clearly detectable in epidermis and in melanocyte cultures as assessed by RNA and western blot analysis. Dystrophin was absent in Duchenne Muscular Dystrophy (DMD) patients melanocytes, and the ultrastructural analysis revealed mitochondrial alterations, similar to those occurring in myoblasts from the same patients. Interestingly, mitochondrial dysfunction of DMD melanocytes reflected the alterations identified in dystrophin-deficient muscle cells. In fact, mitochondria of melanocytes from DMD patients accumulated tetramethylrhodamine methyl ester but, on the contrary of control donor, mitochondria of DMD patients readily depolarized upon the addition of oligomycin, suggesting either that they are maintaining the membrane potential at the expense of glycolytic ATP, or that they are affected by a latent dysfunction unmasked by inhibition of the ATP synthase. Melanocyte cultures can be easily obtained by conventional skin biopsies, less invasive procedure than muscular biopsy, so that they may represent an alternative cellular model to myoblast for studying and monitoring dystrophinopathies also in response to pharmacological treatments.

Determinazione di radicali OH: sintesi di materiali per la modifica di elettrodi di platino e carbone vetroso

Questa tesi descrive lo sviluppo di un elettrodo modificato con un polimero isolante per la determinazione indiretta del radicale OH. I polimeri testati sono stati polifenolo, polipirrolo e polipirrolo sovraoossidato ed il primo è risultato quello con le migliori prestazioni. Il film di modificante è stato depositato per elettropolimerizzazione del fenolo in ambiente acido, su un elettrodo di carbone vetroso (GC) ed è risultato isolante e perfettamente adeso al GC, impedendo il trasferimento di carica alle più comuni sonde redox. L’attacco dei radicali OH, generati dalla reazione di Fenton o dalla fotolisi di H2O2, rimuove parzialmente il polimero dal GC, ripristinando parzialmente il comportamento conduttore dell’elettrodo. L’entità della degradazione del film polifenolico è stata valutata sfruttando la corrente relativa alla sonda redox Ru(NH3)63+, che rappresenta il segnale analitico per la determinazione del radicale OH. L’elettrodo è stato impiegato per stimare le prestazioni di foto catalizzatori a base di nanoparticelle di TiO2, ottenendo risultati correlati a quelli ricavati da un metodo HPLC. Inoltre esso è stato usato per sviluppare una nuova procedura per la determinazione della capacità di scavenging verso i radicali OH, che è stata applicata all’analisi di composti puri e campioni reali. I risultati erano confrontabili con quelli determinati con metodiche standardizzate, comunemente impiegate per la determinazione della capacità antiossidante. Inoltre è stato condotto uno studio riguardante la modifica di un elettrodo di platino con un idrossido misto a strati a base di cobalto e alluminio (LDH). In particolare si sono valutati gli effetti di diversi pretrattamenti del Pt sulle caratteristiche e prestazioni elettrocatalitiche del film di LDH nei confronti dell’ossidazione di anilina, fenolo e acido salicilico. Questi composti possono essere impiegati come molecole sonda per la determinazione del radicale OH e rivestono interesse da un punto di vista elettroanalitico perché portano facilmente alla passivazione della superficie di Pt.

Sequence-controlled synthesis of soluble oligo(p-benzamide)s

This work focused on the synthesis of novel monomers for the design of a series of oligo(p-benzamide)s following two approaches: iterative solution synthesis and automated solid phase protocols. These approaches present a useful method to the sequence-controlled synthesis of side-chain and main-chain functionalized oligomers for the preparation of an immense variety of nanoscaffolds. The challenge in the synthesis of such materials was their modification, while maintaining the characteristic properties (physical-chemical properties, shape persistence and anisotropy). The strategy for the preparation of predictable superstructures was devote to the selective control of noncovalent interactions, monodispersity and monomer sequence. In addition to this, the structure-properties correlation of the prepared rod-like soluble materials was pointed. The first approach involved the solution-based aramide synthesis via introduction of 2,4-dimethoxybenzyl N-amide protective group via an iterative synthetic strategy The second approach focused on the implementation of the salicylic acid scaffold to introduce substituents on the aromatic backbone for the stabilization of the OPBA-rotamers. The prepared oligomers were analyzed regarding their solubility and aggregation properties by systematically changing the degree of rotational freedom of the amide bonds, side chain polarity, monomer sequence and degree of oligomerization. The syntheses were performed on a modified commercial peptide synthesizer using a combination of fluorenylmethoxycarbonyl (Fmoc) and aramide chemistry. The automated synthesis allowed the preparation of aramides with potential applications as nanoscaffolds in supramolecular chemistry, e.g. comb-like-

Synthese und Charakterisierung von zylindrischen Bürsten mit Polypeptidseitenketten

In der vorliegenden Arbeit konnte gezeigt werden, dass durch die grafting-from-Methode verschiedene geschützte Polypeptidbürsten basierend auf L-glutaminsäure, L-asparaginsäure, L-lysin und L-ornithin synthetisch zugänglich sind. Zur Verwirklichung dieser Synthesestrategie wurde mehrstufig ein Makroinitiator auf Basis von N-methacrylamid-1,6-diaminohexan hergestellt, der die ringöffnende Polymerisation von Leuchs´schen Anhydriden zur Entwicklung von geschützten Polypeptidseitenketten initiieren kann. Durch stark saure bzw. alkalische Abspaltbedingungen war es möglich, die Schutzgruppen bei allen geschützten Bürsten bis auf eine Spezies erfolgreich zu entfernen. Weitergehende Untersuchungen an den positiv bzw. negativ geladenen Polyelektrolytbürsten mittels statischer Lichtstreuung und Kapillarelektrophorese zeigten, dass lediglich die Z-geschützten Poly-L-lysinbürsten ohne Kettenabbau entschützt werden konnten. In allen anderen Fällen wurden nach Abspaltung der Schutzgruppen lineare Kettenfragmente detektiert. Durch die Zugabe von NaClO4 oder Methanol zu den wässrigen Lösungen der Poly-L-lysinbürsten konnte mittels CD-Spektroskopie gezeigt werden, dass die Seitenketten von einer ungeordneten Konformation in eine helikale Konformation übergehen. In weiterführenden Experimenten wurde mittels statischer Lichtstreuung, dynamischer Lichtstreuung, SAXS, und AFM-Aufnahmen in Lösung bewiesen, dass die helikale Konformation der Seitenketten eine deutliche Abnahme des Zylinderquerschnitts und des Querschnittträgheitsradius zur Folge hat, die Topologie der Bürste allerdings unverändert bleibt. Weiterhin konnte mittels Kapillarelektrophorese die elektrophoretische Mobilität der Poly-L-lysinbürsten und ihrer linearen Analoga bestimmt werden. Mit diesen Resultaten war es in Kombination mit statischen Lichtstreuexperimenten möglich, die effektive Ladung von linearem und verzweigten Poly-L-lysin nach einer Theorie von Muthukumar zu berechnen. Das Ergebnis dieser Rechnungen bestätigt die Ergebnisse früherer Untersuchungen von Peter Dziezok, der in seiner Dissertation durch Leitfähigkeits und Lichtstreumessungen an linearem PVP und PVP-Bürsten herausfand, dass die effektive Ladung von Polymerbürsten mindestens um einen Faktor 10 kleiner ist als bei den korrespondierenden linearen Analoga.

On-surface chemical reactions on an insulating substrate

Diese Arbeit beschreibt zum ersten Mal die kovalente Verknüpfung organischer Moleküle auf einer Isolatoroberfläche, motiviert im Hinblick auf die Nutzung der Synthesemethode für die molekulare Elektronik und verwandte Anwendungen. Durch die Verwendung der Nichtkontakt-Rasterkraftmikroskopie und der Kelvinprobe-Mikroskopie bei Raumtemperatur wurden grundlegende molekulare Prozesse der Wechselwirkungen zwischen Molekülen und der Calcit(10.4) Oberfläche sowie die chemische Reaktivität der Moleküle auf der Oberfläche analysiert. Das Zusammenspiel zwischen intermolekularen und Molekül-Oberfläche Wechselwirkungen zeigt sich für Biphenyl-4,4'-dicarbonsäure (BPDCA) durch die Koexistenz zweier unterschiedlicher molekularer Strukturen, die einen Einblick in die treibenden Kräfte der molekularen Selbstorganisation bieten. Die sehr ausgeprägte Reihenstruktur basiert auf der optimalen geometrischen Struktur der BPDCA Moleküle zu den Abmessungen des Substrats, während die zweite Struktur durch Wasserstoffbrücken zwischen den Molekülen gekennzeichnet ist. Der Deprotonierungsvorgang von 2,5-Dihydroxybenzoesäure (DHBA)-Molekülen auf Calcit wird bei Zimmertemperatur gezeigt. Zwei Phasen werden beobachtet, die nach Aufbringen der Moleküle koexistieren. Mit der Zeit geht eine bulk-ähnliche Phase in eine stabile, dicht gepackte Phase über. Der Übergang wird durch Betrachtung des Protonierungszustands der Moleküle erklärt. Die bulk-ähnliche Phase benötigt Wasserstoffbrückbindungen zur Strukturbildung. Werden die Moleküle deprotoniert, so wird die resultierende dicht gepackte Phase durch die elektrostatische Wechselwirkung der deprotonierten Carboxylatgruppen mit den Oberflächen-Calciumkationen stabilisiert. 4-Iodbenzoesäure (IBA)-Moleküle bilden auf Calcit nur Inseln an Stufenkanten, was auf die schwache Molekül-Oberflächen-Wechselwirkung zurückzuführen ist. Für einen stärkeren Einfluss des Substrats durchlaufen die Moleküle einen kontrollierten Übergangsschritt vom protonierten zum deprotonierten Zustand. Im deprotonierten Zustand nehmen die Moleküle eine wohldefinierte Adsorptionsposition auf dem Substrat ein. Die deprotonierte Säuregruppe wird ausgenutzt, um die Desorption der halogensubstituierten Benzoesäure-Moleküle bei der thermischer Aktivierung für die Vernetzungsreaktion zu vermeiden. Darüber hinaus wird die Carboxylatgruppe als starker Elektronendonor verwendet um die Phenyl-Halogen-Bindung zu schwächen und somit die homolytische Spaltung dieser Bindung auch bei moderaten Temperaturen zu ermöglichen. Diesem Konzept folgend ist die erste erfolgreiche kovalente Verknüpfung von 2,5-Diiod-benzoesäure, 2,5-Dichlorbenzoesäure, 3,5-Diiod Salicylsäure und 4-Iod-benzoesäure zu durchkonjugierten molekularen Drähten, Zick-Zack-Strukturen sowie Dimere gezeigt durch Ausnutzen von unterschiedlichen Substitutionsposition sowie Ändern der Anzahl der substituierten Halogenatome. Aufbauend auf diesem Erfolg, wird eine zweistufige Vernetzungsreaktion vorgestellt. Zum Induzieren der ortsspezifischen und sequentiellen kovalenten Verknüpfung wird ein Ausgangsmolekül gewählt, das sowohl eine Bromphenyl als auch eine Chlorphenyl Gruppe mit unterschiedlichen Dissoziationsenergien für die homolytische Spaltung besitzt. Die Reaktionsstellen und sequentielle Reihenfolge für die Reaktion sind somit in der molekularen Struktur einkodiert und bisher unerreichte Reaktionspfade können mithilfe der kovalente Verknüpfung organischer Moleküle auf einer Isolatoroberfläche beschritten werden.