1,018 research outputs found
Experimental and theoretical studies of sequence effects on the fluctuation and melting of short DNA molecules
Understanding the melting of short DNA sequences probes DNA at the scale of
the genetic code and raises questions which are very different from those posed
by very long sequences, which have been extensively studied. We investigate
this problem by combining experiments and theory. A new experimental method
allows us to make a mapping of the opening of the guanines along the sequence
as a function of temperature. The results indicate that non-local effects may
be important in DNA because an AT-rich region is able to influence the opening
of a base pair which is about 10 base pairs away. An earlier mesoscopic model
of DNA is modified to correctly describe the time scales associated to the
opening of individual base pairs well below melting, and to properly take into
account the sequence. Using this model to analyze some characteristic sequences
for which detailed experimental data on the melting is available [Montrichok et
al. 2003 Europhys. Lett. {\bf 62} 452], we show that we have to introduce
non-local effects of AT-rich regions to get acceptable results. This brings a
second indication that the influence of these highly fluctuating regions of DNA
on their neighborhood can extend to some distance.Comment: To be published in J. Phys. Condensed Matte
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
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
On the Outside Looking In: An African American Family’s Experience in an Individualized Education Plan Meeting
The current laws that mandate special education originated through the advocacy of families (Turnbull & Turnbull, 1990). Over the years, families have challenged the system to provide free and appropriate public educations for their children. We share, through qualitative measures, the experiences of one African American family and the educators who serve them trying to navigate the system as well as the obstacles they faced. Recommendations for P-12 practice, teacher education, and advocacy efforts are discussed
Mini Max Wallpaper
Mini Max company formulated a problem for the automatic calculation of the number of wallpaper rolls necessary for decorating a room with wallpaper. The final goal is the development of a web-based calculator open for use to both Mini Max staff and the general public. We propose an approach for reducing the studied problem to the one-dimensional cutting-stock problem. We show this in details for the case of plain wallpapers as well as for the case of patterned wallpapers with straight match. The one-dimensional cutting-stock problem can be formulated as a linear integer programming problem. We develop an approach for calculating the needed number of wallpapers for relatively small problems, create an algorithm in a suitable graphical interface and make different tests. The tests show the efficiency of the proposed approach compared with the existent (available) wallpapers’ calculators
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
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
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