Mjerenje prinosa međusustavnog prijelaza s4U u tRNA vremenski-razlučenim izbjeljivanjem

The rare base 4-thiouridine (s4U), present in various transfer RNA (tRNA) molecules from Escherichia coli, occupies usually the strategically important 8 th position between the double helices of the acceptor and the dihydrouridine stems of the cloverleaf. This unusual base is largely used as an intrinsic build-in probe for RNA conformational and RNA(DNA)–protein interaction studies through triplet excited state photochemistry related to covalent adducts formation. Here, by applying laser transient absorption saturation spectroscopy, we measured the intersystem crossing yield ϕST and the excited triplet state absorption εT−T of s4U within tRNA. While the incorporation of s4U in tRNA induced appreciable changes in the latter, no important variation of the intersystem crossing yield was observed, which is in contrasts with the published data.Rijetka baza 4-thiouridine (s4U), koju nalazimo u raznim prijenosnim molekulama RNA (tRNA) Escherichie coli, obično uzima strateški važan 8. položaj između dviju zavojnica primatelja i dihidrouridinskih stapki lista djeteline. Ta se neobična baza najviše rabi kao unutarnja ugradbena proba za proučavanje interakcija konformalne RNA s RNA(DNA)–proteinima preko fotokemije tripletnog uzbuđenog stanja, povezanog sa stvaranjem kovalentnih adukata. U ovom smo radu primjenom laserske prijelazne apsorpcijske spektroskopije sa zasićenjem mjerili prinos međusustavnih prijelaza ϕST i apsorpciju tripletnog stanja εT−T s 4U u tRNA. Dok ugrađivanje s4U u tRNA uzrokuje prilične promjene u tRNA, nismo opazili promjene prinosa međusustavnih prijelaza, što nije u skladu s objavljenim rezultatima

Učinci UV zračenja visokog intenziteta na izdvojen i s dna interkaliran etidium bromid

High-intensity picosecond laser flash photolysis has been used for investigating ethidium bromide (EtBr). The quantum yield of primary photoproducts as a function of the laser intensity has been obtained. DNA intercalated EtBr and water solutions of EtBr have been investigated. The results have been compared. They show that two-photon processes are predominantly responsible for generation of hydrated electron (eaq-). The primary processes of DNA photosensitization have also been discussed.Istraživali smo etidium bromid (EtBr) pomoću pikosekundne bljeskovne fotolize velikog intenziteta. Određeni su kvantni prinosi fotoprodukata u ovisnosti o intenzitetu laserskog snopa. Istraživao se je EtBr u vodenoj otopini i interkalirani s DNA. Rezultati se uspoređuju i oni pokazuju da pretežno dvofotonski procesi tvore hidrirane elektrone eaq-. Raspravljaju se također primarni procesi fotosenzitiranja DNA

Laserska izravna dvofotonska fotoliza guanina u DNK

Nanosecond laser-induced oxidative lesions at guanines within DNA were investigated using sequencing gel electrophoresis analysis. Strong sequence-specific lesions on guanines were revealed by either Fpg or piperidine treatments and assigned to 8-oxoG and oxazolone, respectively. It was shown that both the biphotonic ionization process and the chemical reactivity of the radical cation (G+) are dependent on the DNA sequence. The former were explained by the occurrence of energy and charge migration phenomena, while the latter in terms of local DNA hydration peculiarities.Istraživali smo lomove DNK izazvane nanosekundnim laserskim impulsima primjenom gel elektroforeze za određivanje nizova. Otkrili smo snažne nizovno specifične lomove kod guanina djelovanjem sa Fpg ili piperidinom i oni se pripisuju 8-oxoG odnosno oxazolonu. Pokazali smo da su i dvofotonski ionizacijski proces i kemijska reaktivnost radikala kationa (G+) nizovno ovisni. Prvi se objašnjava selenjem energije i naboja, a drugi kao posebnosti lokalnog hidriranja DNK

Methyl-β-Cyclodextrins Preferentially Remove Cholesterol from the Liquid Disordered Phase in Giant Unilamellar Vesicles

Methyl-β-cyclodextrins (MβCDs) are molecules that are extensively used to remove and to load cholesterol (Chol) from artificial and natural membranes; however, the mechanism of Chol extraction by MβCD from pure lipids or from complex mixtures is not fully understood. One of the outstanding questions in this field is the capability of MβCD to remove Chol from lipid domains having different packing. Here, we investigated the specificity of MβCD to remove Chol from coexisting macrodomains with different lipid packing. We used giant unilamellar vesicles (GUVs) made of 1,2-dioleoylphosphatidylcholine:1,2-dipalmitoylphatidylcholine:free cholesterol, 1:1:1 molar ratio at 27°C. Under these conditions, individual GUVs present Chol distributed into lo and ld phases. The two phases can be distinguished and visualized using Laurdan generalized polarization and two-photon excitation fluorescence microscopy. Our data indicate that MβCD removes Chol preferentially from the more disordered phase. The process of selective Chol removal is dependent on the MβCD concentration. At high concentrations, MβCD also removes phospholipids

Improving Categorisation in Social Media Using Hyperlinks to Structured Data Sources

Abstract. Social media presents unique challenges for topic classifica-tion, including the brevity of posts, the informal nature of conversations, and the frequent reliance on external hyperlinks to give context to a con-versation. In this paper we investigate the usefulness of these external hyperlinks for categorising the topic of individual posts. We focus our analysis on objects that have related metadata available on the Web, either via APIs or as Linked Data. Our experiments show that the in-clusion of metadata from hyperlinked objects in addition to the original post content significantly improved classifier performance on two dis-parate datasets. We found that including selected metadata from APIs and Linked Data gave better results than including text from HTML pages. We investigate how this improvement varies across different top-ics. We also make use of the structure of the data to compare the use-fulness of different types of external metadata for topic classification in a social media dataset

Critique of deinstitutionalisation in postsocialist Central and Eastern Europe

In this paper, we explore critically deinstitutionalisation reform, focusing specifically on the postsocialist region of Central and Eastern Europe (CEE). We argue that deinstitutionalisation in postsocialist CEE has generated re-institutionalising outcomes, including renovation of existing institutions and/or creation of new, smaller settings that have nevertheless reproduced key features of institutional life. To explain these trends, we first consider the historical background of the reform, highlighting the legacy of state socialism and the effects of postsocialist neoliberalisation. We then discuss the impact of ‘external’ drivers of deinstitutionalisation in CEE, particularly the European Union and its funding, as well as human rights discourses incorporated in the UN Convention on the Rights of Persons with Disabilities. The analysis is supported by looking at the current situation in Hungary and Bulgaria through recent reports by local civil society organisations. In conclusion, we propose some definitional tactics for redirecting existing resources towards genuine community-based services