Synthesis and characterization of a metal-salen base pair for the assembly of programmed metal arrays inside the DNA double helix

Base pairing in natural oligonucleotides relies on hydrogen bonding and pi-stacking. Applying coordinative interactions between ligand-like nucleobases and metal cations is a new way of assembling artificial oligonucleotide duplexes. The incorporation of numerous metal-base pairs into oligonucleotides may lead to interesting compounds for nano-technological applications. In this thesis, the synthesis of the salen-metal base pair is described, which comprises preparation of a suitable protected salicylic aldehyde precursor and an organo-cuprate mediated C-glycosidation as the key step. An x-ray structure of the monomeric copper-salen base pair shows a very good geometrical match with natural Watson-Crick base pairs. Up to 10 consecutive salicylic aldehyde-nucleobases could be incorporated into DNA oligonucleotides by means of phosphoramidite chemistry. The synthesized double strands with one ligand show typical B-DNA CD-spectra and distinct melting characteristics. Addition of excess ethylenediamine and 1 eq of Mn2+ or Cu2+ increase the melting temp. by 28 °C and 42 °C, respectively. The complexation of these and other metals was examined by UV-, CD- and EPR-spectroscopy and high res. ESI mass spectrometry. It was possible to stack 10 manganese atoms inside the double helix and to prepare sequence specifically arrays of up to 5 copper ions plus 5 mercury ions inside one duplex

Haavasidoksen vaihto kirurgiseen haavaan : Opetusvideo keskivaiheen sairaanhoitajaopiskelijoille

Tuotokseen painottuvan opinnäytetyön tarkoituksena oli tuottaa Tampereen ammattikorkeakoulun kirurgisen hoitotyön keskivaiheen sairaanhoitajaopiskelijoille opetusvideo, aiheesta haavasidoksen vaihto kirurgiseen haavaan. Opinnäytetyön tehtävinä oli selvittää, millainen on kirurginen haava, millaista aseptiikkaa tarvitaan kirurgisen haavan hoidossa, miten haavasidos vaihdetaan kirurgisen haavaan ja millainen on hyvä opetusvideo. Työn tavoitteena oli tukea sairaanhoitajaopiskelijoiden oppimista liittyen alle 24 tuntia vanhan kirurgisen haavan hoitoon. Opetusvideolla havainnollistettiin haavan sidosvaihdon aseptiikkaa sekä valmistamaan opiskelijaa suunnittelemaan tulevaa haavanhoitoa. Opinnäytetyö toteutettiin toiminnallisena opinnäytetyönä, jonka tuotoksena oli opetusvideo ja kirjallinen raportti. Kirurgisella haavalla tarkoitetaan iholle tehtyä leikkaushaavaa. Kirurginen haava kuuluu pitää peiteltynä 24 tuntia leikkauksesta ja sitä käsitellään mahdollisimman vähän. Yleensä puhdas kirurginen haava paranee ongelmitta, mutta komplikaatioihin kuten verenvuotoon on osattava varautua. Haavan vuotaessa ja sidosten kastuessa haavasidos on vaihdettava pohjia myöten, vaikka haavan sulkemisesta olisi alle 24 tuntia. Tällöin haavasidoksen vaihto tulee tehdä steriilisti. Haavan paranemisen kannalta sairaanhoitajan ammattiosaaminen korostuu, jolloin on osattava kirurgisen haavan peittelyn perusteet. Aseptinen työskentely, haavasidoksen valinta ja tietotaito siitä, milloin haavasidoksen vaihto on tarpeellinen ehkäisevät mahdollisia komplikaatioita, kuten haavainfektioita. Opinnäytetyön tuotoksena valmistui opetusvideo kirjallisen raportin teoriatiedon pohjalta. Video toimii sairaanhoitajaopiskelijoille opetuksen tukena ja havainnollistaa konkreettisesti eri työvaiheita alle 24 tuntia vanhan kirurgisen haavan sidoksen vaihdossa. Opinnäytetyön kirjallista tuotosta ja opetusvideota voidaan hyödyntää kirurgisen hoitotyön opetuksessa. Alle 24 tuntia vanhan kirurgisen haavan sidosvaihdosta ei löydy selkeää ohjeistusta siitä, kuinka toimia, joten opinnäytetyö on hyvä lisämateriaali sairaanhoitajaopiskelijoille. Jatkotutkimusehdotuksena esitetään kvantitatiivista tutkimusta siitä, kuinka työelämässä kirurgisen haavan sidoksen vaihto tapahtuu ja kuinka eri työvaiheet toteutuvat.The aim of this study was to define the concept of a surgical wound, the methods of protection against infections in wound care and how to change the wound dressing for a surgical wound. Moreover, the aim was to produce a suitable educational video in addition to the theoretical part of the study.  The study had a functional approach with the written report and an educational video as a tangible output of the process. The aim of the report and the video was to support the education of nursing students in the care of an under 24-hour-old surgical wound. The educational video presents protection against infections during the change of a wound dressing. It also prepares the student to plan the upcoming wound care.  The surgical wound should be covered up and left untouched for 24 hours after the operation. The wound dressing should be changed thoroughly if the wound bleeds and the dressings get wet even though the operation has been performed less than 24 hours ago. In that case, the change of the dressings should be performed in a sterile manner. Written instructions on changing the surgical wound dressings being somewhat limited, this thesis provides important information about surgical wound care in this particular respect. There is a need for a further quantitative study about the various stages in changing the surgical wound dressings in hospital settings

Guest-modulated circularly polarized luminescence by ligand-to-ligand chirality transfer in heteroleptic Pd(II) coordination cages

Multicomponent metallo-supramolecular assembly allows to rationally combine different building blocks. Discrete multifunctional hosts with an accessible cavity can be prepared in a non-statistical fashion. We employ our shape-complementary assembly (SCA) method to achieve for the first time integrative self-sorting of heteroleptic PdII cages showing guest-tunable circularly polarized luminescence (CPL). An enantiopure helicene-based ligand (M or P configuration) is coupled with a non-chiral emissive fluorenone-based ligand (A or B) to form a series of Pd2L2L’2 assemblies. The modular strategy allows to impart the chiral information of the helicenes to the overall supramolecular system, resulting in CPL from the non-chiral component. Guest binding results in a 4-fold increase of CPL intensity. The principle offers potential to generate libraries of multifunctional materials with applications in molecular recognition, enantioselective photo-redox catalysis and information processing

Multi-stimuli control over assembly and guest binding in metallo-supramolecular hosts based on dithienylethene photoswitches

It is difficult to assemble multi-component metallo-supramolecular architectures in a non-statistical fashion, whichlimits their development toward functional materials. Herein, wereport a system of interconverting bowls and cages that are able torespond to various selective stimuli (light, ligands, anions), basedon the self-assembly of a photochromic dithienylethene (DTE)ligand,La, with PdIIcations. By combining the concept of“coordination sphere engineering”, relying on bulky quinolinedonors, with reversible photoswitching between the ligand’s open(o-La) and closed (c-La) forms, a [Pd2(o-La)4] cage (o-C) and a[Pd2(c-La)3] bowl (c-B) were obtained, respectively. This structuralrearrangement modulates the system’s guest uptake capabilities.Among three bis-sulfonate guests (G1,G2, andG3), the cage canencapsulate only the smallest (G1), while the bowl binds all of them. Bowlc-Bwas further used to synthesize a series of heterolepticcages, [Pd2LA3LB], representing a motif never reported before. Additional ligands (Lc‑f), with short or long arms, tune the cavity size,thus enabling or preventing guest uptake. Addition of Br−/Ag+makes it possible to change the overall charge, again triggering guestuptake and release, as well as fourth ligand de-/recomplexation. In combination, site-selective introduction of functionality andapplication of external stimuli lead to an intricate system of hosts with different guest preferences. A high degree of complexity isachieved through cooperativity between only a few components

Precise distance measurements in DNA G-quadruplex dimers and sandwich complexes by pulsed dipolar EPR spectroscopy

DNA G-quadruplexes show a pronounced tendency to form higher-order structures, such as π-stacked dimers and aggregates with aromatic binding partners. Reliable methods for determining the structure of these non-covalent adducts are scarce. Here, we use artificial square-planar Cu(pyridine)4 complexes, covalently incorporated into tetramolecular G-quadruplexes, as rigid spin labels for detecting dimeric structures and measuring intermolecular Cu2+–Cu2+ distances via pulsed dipolar EPR spectroscopy. A series of G-quadruplex dimers of different spatial dimensions, formed in tail-to-tail or head-to-head stacking mode, were unambiguously distinguished. Measured distances are in full agreement with results of molecular dynamics simulations. Furthermore, intercalation of two well-known G-quadruplex binders, PIPER and telomestatin, into G-quadruplex dimers resulting in sandwich complexes was investigated, and previously unknown binding modes were discovered. Additionally, we present evidence that free G-tetrads also intercalate into dimers. Our transition metal labeling approach, combined with pulsed EPR spectroscopy, opens new possibilities for examining structures of non-covalent DNA aggregates

Localized transverse bursts in inclined layer convection

We investigate a novel bursting state in inclined layer thermal convection in which convection rolls exhibit intermittent, localized, transverse bursts. With increasing temperature difference, the bursts increase in duration and number while exhibiting a characteristic wavenumber, magnitude, and size. We propose a mechanism which describes the duration of the observed bursting intervals and compare our results to bursting processes in other systems.Comment: 4 pages, 8 figure

Integrative assembly of heteroleptic tetrahedra controlled by backbone steric bulk

A bent fluorenone-based dipyridyl ligand LA reacts with PdII cations to a solvent-dependent dynamic library of [PdnL2n] assemblies, constituted by a [Pd3LA6] ring and a [Pd4LA8] tetrahedron as major components, and a [Pd6LA12] octahedron as minor component. Introduction of backbone steric hindrance in ligand LB allows exclusive formation of the [Pd6LB12] octahedron. Combining equimolar amounts of both ligands results in integrative self-sorting to give an unprecedented [Pd4LA4LB4] heteroleptic tetrahedron. Key to the non-statistical assembly outcome is exploiting the structural peculiarity of the [Pd4L8] tetrahedral topology, where the four lean ligands occupy two doubly bridged edges and the bulky ligands span the four remaining, singly bridged edges. Hence, the system finds a compromise between the entropic drive to form an assembly smaller than the octahedron and the enthalpic prohibition of pairing two bulky ligands on the same edge of the triangular ring. The emission of luminescent LA is maintained in both homoleptic [Pd3LA6] and heteroleptic [Pd4LA4LB4]

Tunable fullerene affinity of cages, bowls and rings assembled by Pd(II) coordination sphere engineering

For metal‐mediated host compounds, the development of strategies to reduce symmetry and introduce multiple functionalities in a non‐statistical way is a challenging task. We show that the introduction of steric stress around the coordination environment of square‐planar Pd(II) cations and bis‐monodentate nitrogen donor ligands allows to control the size and shape of the assembly product, from [Pd2L4] cages over [Pd2L3] bowl‐shaped structures to [Pd2L2] rings. Therefore, banana‐shaped ligand backbones were equipped with pyridines, two different quinoline isomers and acridine, the latter three introducing steric congestion through hydrogen substituents on annelated benzene rings. Differing behavior of the four resulting hosts towards the binding of C60 and C70 fullerenes was studied and related to structural differences by NMR spectroscopy, mass spectrometry and single crystal X‐ray diffraction. The three cages based on pyridine, 6‐quinoline or 3‐quinoline donors were found to either bind C60, C70 or no fullerene at all

Backbone-bridging promotes diversity in heteroleptic cages

The combination of shape-complementary bis-monodentate ligands LA and LB with PdII cations yields heteroleptic cages cis-[Pd2LA2LB2] by self-sorting. Herein, we report how such assemblies can be diversified by introduction of covalent backbone bridges between two LA units. Together with solvent and guest effects, the flexibility of these linkers can modulate nuclearity, topology, and number of cavities in a family of four structurally diverse assemblies. Ligand LA1, with flexible linker, reacts in CH3CN with its LB counterpart to a tetranuclear dimer D1. In DMSO, however, a trinuclear pseudo-tetrahedron T1 is formed. The product of LA2, with rigid linker, looks similar to D1, but with a rotated ligand arrangement. In presence of an anionic guest, this dimer D2 transforms and a hexanuclear prismatic barrel P2 crystallizes. We demonstrate how controlling a ligand's coordination mode can trigger structural differentiation and increase complexity in metallo-supramolecular assembly

Substrate and product binding inside a stimuli-responsive coordination cage acting as singlet oxygen photosensitizer

An acridone-based, interpenetrated double cage [3BF4Pd4L8] acts as a photosensitizer for generating singlet oxygen which adds to 1,3-cyclohexadiene in a [2+4] hetero-Diels-Alder reaction to form 2,3-dioxabicyclo[2.2.2]oct-5-ene. Photocatalytic activity was exclusively observed for the assembled cage, whereas the free organic ligand L decomposes upon irradiation. While cage [3BF4Pd4L8] does not accept any organic guests, NMR, MS and single crystal X-ray results reveal that both substrate and product are readily encapsulated in the central pocket of its chloride-activated form [2Cl@Pd4L8]. The system combines multiple functions (photosensitization, allosteric activation and guest uptake) within a structurally complex, mechanically-bound self-assembly built up from a simple and readily accessible ligand