Affinity of Talin-1 for the β3-Integrin Cytosolic Domain is Modulated by its Phospholipid Bilayer Environment

Binding of the talin-1 FERM (4.1/ezrin/radixin/moesin) domain to the β3 cytosolic tail causes activation of the integrin αIIbβ3. The FERM domain also binds to acidic phospholipids. Although much is known about the interaction of talin-1 with integrins and lipids, the relative contribution of each interaction to integrin regulation and possible synergy between them remain to be clarified. Here, we examined the thermodynamic interplay between FERM domain binding to phospholipid bilayers and to its binding sites in the β3 tail. We found that although both the F0F1 and F2F3 subdomains of the talin-1 FERM domain bind acidic bilayers, the full-length FERM domain binds with an affinity similar to F2F3, indicating that F0F1 contributes little to the overall interaction. When free in solution, the β3 tail has weak affinity for the FERM domain. However, appending the tail to acidic phospholipids increased its affinity for the FERM domain by three orders of magnitude. Nonetheless, the affinity of the FERM for the appended tail was similar to its affinity for binding to bilayers alone. Thus, talin-1 binding to the β3 tail is a ternary interaction dominated by a favorable surface interaction with phospholipid bilayers and set by lipid composition. Nonetheless, interactions between the FERM domain, the β3 tail, and lipid bilayers are not optimized for a high-affinity synergistic interaction, even at the membrane surface. Instead, the interactions appear to be tuned in such a way that the equilibrium between inactive and active integrin conformations can be readily regulated

Aggregatibacter Actinomycetemcomitans Leukotoxin Causes Activation of Lymphocyte Function-Associated Antigen 1

Repeats-in-toxin leukotoxin (LtxA) produced by the oral bacterium Aggregatibacter actinomycetemcomitans kills human leukocytes in a lymphocyte function-associated antigen 1 (LFA-1, integrin α L /β 2 )-dependent manner, although the mechanism for this interaction has not been identified. The LtxA internalisation by LFA-1-expressing cells was explored with florescence resonance energy transfer (FRET) microscopy using a cell line that expresses LFA-1 with a cyan fluorescent protein-tagged cytosolic α L domain and a yellow fluorescent protein-tagged β 2 domain. Phorbol 12-myristate 13-acetate activation of LFA-1 caused transient cytosolic domain separation. However, addition of LtxA resulted in an increase in FRET, indicating that LtxA brings the cytosolic domains closer together, compared with the inactive state. Unlike activation, this effect was not transient, lasting more than 30 min. Equilibrium constants of LtxA binding to the cytoplasmic domains of both α L and β 2 were determined using surface plasmon resonance. LtxA has a strong affinity for the cytosolic domains of both the α L and β 2 subunits (K d = 15 and 4.2 nM, respectively) and a significantly lower affinity for the cytoplasmic domains of other integrin α M , α X , and β 3 subunits (K d = 400, 180, and 230 nM, respectively), used as controls. Peptide fragments of α L and β 2 show that LtxA binds membrane-proximal domain of α L and intermediate domain of β 2 . © 2018 John Wiley & Sons Lt

Solid-phase bio-organic synthesis to create intelligent surfaces

This thesis investigates three different surface modifications, and the route to design and synthesize them. The thesis is therefore divided into three sub- projects. (i.) Design and synthesis of a peptide which secondary structure could be controlled by a negatively charged surface. (ii.) Design and synthesis of a cyclic peptide, that would self-organize prior to surface interaction, using the type I anti-freeze protein of a winter flounder as template. (iii.) The use of solid-phase synthesis to make the synthesis of SAM-molecules easier

Reduceringav känslig information i loggfiler

Information about   companies’ internal networks and structures is something that normally is   desired to be hidden from outsiders. By denying this information from   non-authorized personnel, potential attackers will find it more difficult to   find ways into the network and find attractive targets. Saab is a   manufacturer of defense material and desires to obscure its internal   structures. One of the aims of this project has been to examine what   information on Saabs internal network and structures is given to suppliers of   IT hardware when that supplier’s diagnostic tool is used. This information   has been acquired by interviewing staff responsible for maintenance and   installation of IT hardware and by examining the log files resulting from the   diagnostic tool. A research has   been done on what information is generally considered sensitive and what   existing tools are available that can handle this sensitive information.   Another goal has been to produce software that assists in searching for and   replacing information that is deemed to be sensitive. The software has been   produced using the classic waterfall model, where the separate phases are   clearly defined and separated from each other. The finished application has   been verified in its function against several types of hardware and verified   to run on two different operating systems, Windows and Ubuntu. The result from   running the application is that all MAC/IP-addresses are removed from the log   files, together with user accounts and server names. Java was used as the   programming language and the primary function is performed by Java’s classes   Pattern and Matcher, which are responsible for searching for information and   replacing that information. Besides a working application, the project has delivered   a class diagram, a flow chart and test results. Also, several suggestions on   how the work can move forward have been made.Information om företags interna nätverk och struktur   är något som vanligtvis i mesta möjliga mån önskas vara dolt för utomstående.   Genom att dölja denna information görs det svårare för potentiella angripare   att hitta både vägar in och åtråvärda målytor. Saab är en tillverkare av försvarsmateriel och har   stort intresse av att dölja sina interna strukturer. Målet med detta projekt   har varit att först undersöka vad för information om Saabs interna nätverk   som lämnas ut till hårdvaruleverantör när leverantörens diagnostikverktyg   körs. Denna information har erhållits med ledning av intervjuer med personal   som är ansvariga för underhåll och installation av hårdvara samt även genom   undersökning av de loggfiler som resulterar från diagnostikverktyget. En undersökning har gjorts om vilken information som   anses som känslig och vilka färdiga verktyg som finns för att hantera detta.   Vidare har sedan ett förslag på programvarustöd tagits fram, som syftar till   att söka upp och begränsa den information som bedömts som känslig.   Programvarustödet har utvecklats enligt den klassiska vattenfallsmodellen,   där projektets olika faser är tydligt avgränsade från varandra. Den färdiga   applikationen har verifierats i sin funktion mot ett flertal olika   hårdvarumodeller och även på två olika operativsystem, Windows och Ubuntu. Resultatet av att köra applikationen är att   MAC/IP-adresser tas bort från loggfilerna tillsammans med kontonamn och   servernamn. Java används som programmeringsspråk och det centrala arbetet   utgörs av Javas klasser Pattern och Matcher, som utför sökning och ersättning   av känslig information. Projektet har förutom en körbar Java-applikation,   även levererat klassdiagram, flödesdiagram och testrapporter. Dessutom har   ett antal förslag på fortsatt arbete tagits fram

Structural and Functional Studies of De Novo Designed Peptides at Surfaces

The work presented in this thesis deals with the structural and functional properties of peptides at surfaces. The interaction of peptides with surfaces is an ever so common occurrence in our every day life, from the bug squashed on the windshield of our car to the barnacle on our boat, and from the blood plasma used in the hospital to the proteins in our cells. The effect these occurrences has on our lives is diverse, the bug is annoying whereas the barnacle settlement of ship hull is costly for marine transportation, the blood plasma contains components of vital importance for our immunological defense system and the proteins in our cells are crucial for regulatory processes and life.One part of this thesis, performed as a part of the EU-founded project AMBIO, deals with the concept of marine biofouling. A number of short peptides have been designed, synthesized, and used to investigate their effect on the settlement on marine biofoulers, such as the Ulva linza algae and the Navicula diatom, on template surfaces coated with thin layers of these molecules. The surfaces have been thoroughly investigated with respect of their physio-chemical properties before and after submersion in artificial seawater and ultimately in suspensions containing the organisms. The most interesting results were obtained with an arginine-rich peptide coating that when introduced to Ulva linza zoospores, displayed extensive settlement, compared to reference surfaces. In addition, a large fraction of the settled spores had an abnormal morphology.The other part of this thesis is focused on designed peptides that when adsorbed on a negatively charged surface adopts a well-defined secondary structure, either α-helical or β-sheet. Precisely placed amino acids in the peptides will strongly disfavor structure in solution, primarily due to electrostatic repulsion, but when the peptides are adsorbed on the negatively charged surfaces, they adopt a well-defined secondary structure due to ion pair bonding. These interactions have been thoroughly investigated by systematic variations of the side-chains. In order to determine the factors contributing to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, and 5) incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different interaction partners have also been investigated. It has also been shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both bionanotechnology and medicine

De Novo Design and Characterization of Surface Binding Peptides - Steps toward Functional Surfaces

The ability to create surfaces with well-defined chemical properties is a major research field. One possibility to do this is to design peptides that bind with a specific secondary structure to silica nanoparticles. The peptides discussed in this thesis are constructed to be random coil in solution, but are “forced” to become helical when adsorbed to the particles. The positively charged side-chains on the peptides strongly disfavor an ordered structure in solution due to electrostatic repulsion. When the peptides are introduced to the particles these charges will strongly favor the structure because of ion pair bonding between the peptide and the negatively charged nanoparticles. The peptide-nanoparticle system has been thoroughly investigated by systematic variations of the side-chains. In order to determine which factors that contributes to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, 5) peptide length, and 6) by incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different nanoparticle curvature have also been investigated. It will also be shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both nanotechnology and medicine

Produktplacering i en virtuell värld

Spelmarknaden är en mediekanal som enligt många en stor potential och många spännande möjligheter inom marknadsföring. De stora Internetvärldarna är en starkt växande variant av mediekanal där enorma mängder deltagare kopplar upp sig mot en och samma server där de interagerar med miljön och med varandra. Det speciella med produktplacering i just virtuella världar är att den kan utformas dynamiskt och med en kontinuerlig uppdatering beroende på marknadens reaktioner och olika demografiska skillnader, vilket är av intresse när det gäller produktplacering. Syftet med uppsatsen är att sätta sig in i de specifika omständigheter som råder i en virtuell värld och däri studera möjligheter för produktplacering. Vi har valt att genom en fallstudie studera den virtuella världen Entropia Universe. Miljön är framtiden på en annan planet och världen saknar spelmoment vilket är det främsta skälet till att Entropia Universe själva inte vill kalla sig ett spel, utan en virtuell värld. Det är den första virtuella världen som är direkt kopplad till den verkliga ekonomin vilket innebär att de virtuella produkterna i Entropia Universe också har ett värde i vår verkliga värld. Den övergripande slutsatsen vi drar av vårt arbete är att den virtuella värden till stor del påminner om vår verkliga och det finns goda möjligheter för produktplacering att fungera i en virtuell värld. Produktplaceringen behöver vara mer noggrann/försiktig i sin placering för att inte placera produkten på ett sådant sätt att det stör mottagaren då chansen att lyckas och misslyckas med en produktplacering är betydligt större i den virtuella världen. Vi anser vidare att kopplingen till verklig valuta skapar nya möjligheter för en effektiv produktplacering