Näkövammaisen käyttäjän kohtaamat haasteet verkkopalveluiden käytön yhteydessä käytettävyyden ja tietoturvan näkökulmista ja ratkaisumahdollisuuksia

Tiivistelmä. Tutkielman tarkoituksena oli koota tietoa näytönlukijaan turvautuvien Internetin käyttäjien kokemista ongelmista heidän asioidessaan verkkosivustoilla, mistä ne johtuvat ja miten saavutettavuutta voi parantaa. Lisäksi tutkielma otti kantaa riittämättömän saavutettavuuden vaikutukseen tietoturvaan. Tutkielma toteutettiin kirjallisuuskatsauksena, johon valitut 21 empiiristä artikkelia etsittiin Google Scholarista. Empiiristen tutkimuksen lisäksi kirjallisuuskatsauksen tueksi valittiin lähteitä, jotka eivät ole hyödyntäneet empiiristä tutkimusta. Sellaisia lähteitä olivat teokset, jotka käsittelivät aihetta yleisluontoisesti tai pelkän kirjallisuuskatsauksen avulla ilman, että omaa tutkimusta oli tehty. Empiiriseksi tutkimukseksi laskettiin kyselyn tai haastattelun toteutus tai käyttäjien havainnointi jossain yhteydessä. Selvisi, että suurimpia ongelmia näkövammaisille Internetin käyttäjille ovat vaihtoehtoisten kuvauksien puuttuminen verkkosivun elementeistä, elementtien epäselvä tai puuttuva otsikointi sekä elementtien sekava asettelu tai asettelun epähierarkkisuus. Ongelmia aiheuttavat myös näytönlukijan luettavissa olevan palautteen puute käyttäjän suorittaessa toimintoa tai toiminnon. Tietoturvaan liittyvät ongelmat koskivat lähinnä sitä, että käyttäjät saattavat huonon saavutettavuuden takia joutua pyytämään ulkopuolisen apua arkaluontoisia tietoja sisältävän palvelun käytössä tai heillä ei ole keinoja tunnistaa verkkosivuston epäluotettavuutta. Moni saavutettavuusongelma olisi ratkaistavissa paremmalla WCAG-standardien noudattamisella ja web-kehittäjien kouluttamisella. Esteenä sille saattavat kuitenkin olla ajan tai asiakas- tai kehittäjäorganisaation kiinnostuksen puute. Toisaalta saavutettavuusongelmia voi korjata lainsäädännön keinoin. Tietoturvan erityisesti huomioon ottavien saavutettavuusstandardien luonnille on myös tarve. Tutkielma toi tietoa siitä, mitä ongelmia näkövammaiset käyttäjät kokevat käyttäessään verkkosivustoja ja miten ongelmiin voisi puuttua. Se ei kuitenkaan tarjoa täydellistä katsausta saavutettavuusongelmiin ja niiden ratkaisuun, vaan keskittyy valittujen lähteiden referointiin. Tuloksia voivat hyödyntää verkkosivustojen kehityksessä työskentelevät ICT-alan ammattilaiset

Characterization of the first beta-class carbonic anhydrase from an arthropod (Drosophila melanogaster) and phylogenetic analysis of beta-class carbonic anhydrases in invertebrates

BACKGROUND: The beta-carbonic anhydrase (CA, EC 4.2.1.1) enzymes have been reported in a variety of organisms, but their existence in animals has been unclear. The purpose of the present study was to perform extensive sequence analysis to show that the beta-CAs are present in invertebrates and to clone and characterize a member of this enzyme family from a representative model organism of the animal kingdom, e.g., Drosophila melanogaster. RESULTS: The novel beta-CA gene, here named DmBCA, was identified from FlyBase, and its orthologs were searched and reconstructed from sequence databases, confirming the presence of beta-CA sequences in 55 metazoan species. The corresponding recombinant enzyme was produced in Sf9 insect cells, purified, kinetically characterized, and its inhibition was investigated with a series of simple, inorganic anions. Holoenzyme molecular mass was defined by dynamic light scattering analysis and gel filtration, and the results suggested that the holoenzyme is a dimer. Double immunostaining confirmed predictions based on sequence analysis and localized DmBCA protein to mitochondria. The enzyme showed high CO2 hydratase activity, with a kcat of 9.5 x 105 s-1 and a kcat/KM of 1.1 x 108 M-1s-1. DmBCA was appreciably inhibited by the clinically-used sulfonamide acetazolamide, with an inhibition constant of 49 nM. It was moderately inhibited by halides, pseudohalides, hydrogen sulfide, bisulfite and sulfate (KI values of 0.67 - 1.36 mM) and more potently by sulfamide (KI of 0.15 mM). Bicarbonate, nitrate, nitrite and phenylarsonic/boronic acids were much weaker inhibitors (KIs of 26.9 - 43.7 mM). CONCLUSIONS: The Drosophila beta-CA represents a highly active mitochondrial enzyme that is a potential model enzyme for anti-parasitic drug development

Growth of immobilized DNA by polymerase: bridging nanoelectrodes with individual dsDNA molecules

We present a method for controlled connection of gold electrodes with dsDNA molecules (locally on a chip) by utilizing polymerase to elongate single-stranded DNA primers attached to the electrodes. Thiol-modified oligonucleotides are directed and immobilized to nanoscale electrodes by means of dielectrophoretic trapping, and extended in a procedure mimicking PCR, finally forming a complete dsDNA molecule bridging the gap between the electrodes. The technique opens up opportunities for building from the bottom-up, for detection and sensing applications, and also for molecular electronics.Comment: 5 pages, 3 figures; Nanoscale (2011

Construction of Chimeric Dual-Chain Avidin by Tandem Fusion of the Related Avidins

BACKGROUND: Avidin is a chicken egg-white protein with high affinity to vitamin H, also known as D-biotin. Many applications in life science research are based on this strong interaction. Avidin is a homotetrameric protein, which promotes its modification to symmetrical entities. Dual-chain avidin, a genetically engineered avidin form, has two circularly permuted chicken avidin monomers that are tandem-fused into one polypeptide chain. This form of avidin enables independent modification of the two domains, including the two biotin-binding pockets; however, decreased yields in protein production, compared to wt avidin, and complicated genetic manipulation of two highly similar DNA sequences in the tandem gene have limited the use of dual-chain avidin in biotechnological applications. PRINCIPAL FINDINGS: To overcome challenges associated with the original dual-chain avidin, we developed chimeric dual-chain avidin, which is a tandem fusion of avidin and avidin-related protein 4 (AVR4), another member of the chicken avidin gene family. We observed an increase in protein production and better thermal stability, compared with the original dual-chain avidin. Additionally, PCR amplification of the hybrid gene was more efficient, thus enabling more convenient and straightforward modification of the dual-chain avidin. When studied closer, the generated chimeric dual-chain avidin showed biphasic biotin dissociation. SIGNIFICANCE: The improved dual-chain avidin introduced here increases its potential for future applications. This molecule offers a valuable base for developing bi-functional avidin tools for bioseparation, carrier proteins, and nanoscale adapters. Additionally, this strategy could be helpful when generating hetero-oligomers from other oligomeric proteins with high structural similarity

Environmental spaces for palsas and peat plateaus are disappearing at a circumpolar scale

Abstract Anthropogenic climate change threatens northern permafrost environments. This compromises the existence of permafrost landforms, such as palsas and peat plateaus, which have been assessed to be critically endangered habitats. In this study, we integrated geospatial datasets and statistical methods to model the suitable environments for palsas and peat plateaus across the Northern Hemisphere permafrost region. The models were calibrated using data from years 1950–2000. The effects of climate change on the suitable environments for the landforms were assessed by using low-, moderate-, and high-emissions scenarios (Representative Concentration Pathway climate scenarios: RCP2.6, RCP4.5, and RCP8.5, respectively) for two periods (2041–2060 and 2061–2080). Hotspots for palsa and peat plateau environments occurred in northern Europe, western Siberia, and subarctic Canada. Climate change was predicted to cause an almost complete loss (decrease of 98.2 %) of suitable environmental spaces under the high-emissions scenario by 2061–2080, while under low- and moderate-emissions scenarios the predicted loss was 76.3 % and 89.3 % respectively. Our modeling results are in line with previously published thermokarst data pointing out areas of recent degradation of palsa and peat plateau environments. Our results provide new insights into the distribution of the permafrost landforms in less studied areas such as central and eastern Siberia. In addition, the predictions provide new understanding of the changing geoecological conditions of the circumpolar region with important implications for greenhouse gas emissions

Toward Single Electron Nanoelectronics Using Self-Assembled DNA Structure

DNA based structures offer an adaptable and robust way to develop customized nanostructures for various purposes in bionanotechnology. One main aim in this field is to develop a DNA nanobreadboard for a controllable attachment of nanoparticles or biomolecules to form specific nanoelectronic devices. Here we conjugate three gold nanoparticles on a defined size TX-tile assembly into a linear pattern to form nanometer scale isolated islands that could be utilized in a room temperature single electron transistor. To demonstrate this, conjugated structures were trapped using dielectrophoresis for current–voltage characterization. After trapping only high resistance behavior was observed. However, after extending the islands by chemical growth of gold, several structures exhibited Coulomb blockade behavior from 4.2 K up to room temperature, which gives a good indication that self-assembled DNA structures could be used for nanoelectronic patterning and single electron devices

Extended materials and methods and additional results to 'Geodiversity data for Europe'

Supplementary file includes geodiversity source data details and maps (Appendix 1), extended information on geodiversity calculation (Appendix 2), results on European geodiversity at 10-km resolution (Appendix 3), geodiversity maps for Finland at 1-km resolution (Appendix 4), and geodiversity maps for Switzerland at 10-km resolution (Appendix 5)

Structural characterization of core-bradavidin in complex with biotin

<div><p>Bradavidin is a tetrameric biotin-binding protein similar to chicken avidin and bacterial streptavidin, and was originally cloned from the nitrogen-fixing bacteria <i>Bradyrhizobium diazoefficiens</i>. We have previously reported the crystal structure of the full-length, wild-type (wt) bradavidin with 138 amino acids, where the C-terminal residues Gly129-Lys138 (“Brad-tag”) act as an intrinsic ligand (<i>i</i>.<i>e</i>. Gly129-Lys138 bind into the biotin-binding site of an adjacent subunit within the same tetramer) and has potential as an affinity tag for biotechnological purposes. Here, the X-ray structure of core-bradavidin lacking the C-terminal residues Gly114-Lys138, and hence missing the Brad-tag, was crystallized in complex with biotin at 1.60 Å resolution [PDB:4BBO]. We also report a homology model of rhodavidin, an avidin-like protein from <i>Rhodopseudomonas palustris</i>, and of an avidin-like protein from <i>Bradyrhizobium sp</i>. Ai1a-2, both of which have the Brad-tag sequence at their C-terminus. Moreover, core-bradavidin V1, an engineered variant of the original core-bradavidin, was also expressed at high levels in <i>E</i>. <i>coli</i>, as well as a double mutant (Cys39Ala and Cys69Ala) of core-bradavidin (CC mutant). Our data help us to further engineer the core-bradavidin–Brad-tag pair for biotechnological assays and chemical biology applications, and provide deeper insight into the biotin-binding mode of bradavidin.</p></div