| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Enander, Karin, 1972-, et al.
(författare)
-
A peptide-based, ratiometric biosensor construct for direct fluorescence detection of a protein analyte
- 2008
-
Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 19:9, s. 1864-1870
-
Tidskriftsartikel (refereegranskat)abstract
- We present the design, synthesis, and functional evaluation of peptide-based fluorescent constructs for wavelength-ratiometric biosensing of a protein analyte. The concept was shown using the high-affinity model interaction between the 18 amino acid peptide pTMVP and a recombinant antibody fragment, Fab57P. pTMVP was functionalized in two different positions with 6-bromomethyl-2-(2-furanyl)-3-hydroxychromone, an environmentally sensitive fluorophore with a two-band emission. The equilibrium dissociation constant of the interaction between pTMVP and Fab57P was largely preserved upon labeling. The biosensor ability of the labeled peptide constructs was evaluated in terms of the relative intensity change of the emission bands from the normal (N*) and tautomer (T*) excited-state species of the fluorophore (IN*/IT*) upon binding of Fab57P. When the peptide was labeled in the C terminus, the IN*/I T* ratio changed by 40% upon analyte binding, while labeling close to the residues most important for binding resulted in a construct that completely lacked ratiometric biosensor ability. Integrated biosensor elements for reagentless detection, where peptides and ratiometric fluorophores are combined to ensure robustness in both recognition and signaling, are expected to become an important contribution to the design of future protein quantification assays in immobilized formats. © 2008 American Chemical Society.
|
|
| 8. |
- Enander, Karin, 1972-, et al.
(författare)
-
A versatile polypeptide platform for integrated recognition and reporting : affinity arrays for protein-ligand interaction analysis
- 2004
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 10:10, s. 2375-2385
-
Tidskriftsartikel (refereegranskat)abstract
- A molecular platform for protein detection and quantification is reported in which recognition has been integrated with direct monitoring of target-protein binding. The platform is based on a versatile 42-residue helix–loop–helix polypeptide that dimerizes to form four-helix bundles and allows site-selective modification with recognition and reporter elements on the side chains of individually addressable lysine residues. The well-characterized interaction between the model target-protein carbonic anhydrase and its inhibitor benzenesulfonamide was used for a proof-of-concept demonstration. An affinity array was designed where benzenesulfonamide derivatives with aliphatic or oligoglycine spacers and a fluorescent dansyl reporter group were introduced into the scaffold. The affinities of the array members for human carbonic anhydrase II (HCAII) were determined by titration with the target protein and were found to be highly affected by the properties of the spacers (dissociation constant Kd=0.02–3 μM). The affinity of HCAII for acetazolamide (Kd=4 nM) was determined in a competition experiment with one of the benzenesulfonamide array members to address the possibility of screening substance libraries for new target-protein binders. Also, successful affinity discrimination between different carbonic anhydrase isozymes highlighted the possibility of performing future isoform-expression profiling. Our platform is predicted to become a flexible tool for a variety of biosensor and protein-microarray applications within biochemistry, diagnostics and pharmaceutical chemistry.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
- Enander, Karin, 1972-
(författare)
-
Folded polypeptide scaffolds for biosensor and biochip applications : design, synthesis, functionalisation and characterisation
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the design, synthesis and evaluation of functional molecular units intended for use in biosensor and microarray applications. A flexible, synthetic helix-loop-helix polypeptide that dimerises to form four-helix bundles was used as a scaffold and was modified with affinity ligands and fluorescent probes to specifically bind a target biomolecule and report on this event in an integrated process. The well-characterised binding of carbonic anhydrase by its benzenesulphonamide inhibitor was employed as a model interaction, and the emission intensity of the probe(s) was found to correlate with carbonic anhydrase concentration. A molecular array, spanning two orders of magnitude in affmity and useful for one-step target quantification, was designed by varying the spacer of the benzenesulphonamide derivative. The scaffold itself was found to contribute to binding, expanding the parameters available for affmity modulation. In a separate study focused on the interaction model system, it was revealed that a destabilising point mutation distant from the carbonic anhydrase active site resulted in faster dissociation rates of the benzenesulphonamide ligand. and that this effect was mediated by increased molecular dynamics caused by destabilisation.The fluorescence intensity difference displayed by free and target-bound peptides was found to be critically dependent on the position of the probe(s) in the scaffold, showing that the polypeptide fold, providing directionality of incorporated moieties, contributed considerably to peptide function. Dual labelling of the scaffold with different probes in positions where they displayed increased intensity in the corresponding single-probe peptides resulted in a synergistic emission increase upon target protein binding, significantly enhancing sensitivity. The peptides were shown to bind the target protein as monomers, and the molecular basis for sensing was a combination of specific peptide-protein interactions and dimer dissociation. The photochemical crosstalk between the probes was interrupted upon expulsion of one of the monomers upon binding.Strategies for thiol-dependent attachment of the peptides to modified gold surfaces were explored, and folding of immobilised scaffolds was demonstrated in the case of a model system with controllable dirnerisation properties. Results indicating that the sensing ability was retained upon peptide immobilisation were encouraging and prompted future studies on the relation between peptide structure and function, aiming at successful sensor surface and rnicroarray designs for the identification, quantification and characterisation of a wide variety of target biomolecules.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- Riepl, M, et al.
(författare)
-
Functionalized surfaces of mixed alkanethiols on gold as a platform for oligonucleotide microarrays
- 2002
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:18, s. 7016-7023
-
Tidskriftsartikel (refereegranskat)abstract
- Mixed self-assembled monolayers of biotinylated- and ethylene glycol-terminated long-chain alkanethiols were prepared on gold surfaces in an attempt to develop a reliable protocol for immobilization of streptavidin. A broad range of surface analytical techniques including ellipsometry, atomic force microscopy, and infrared, fluorescence, and X-ray photoelectron spectroscopy were used to characterize the SAMs before and after immobilization of streptavidin. The first part of the work was focused on finding the mixing conditions that lead to optimum binding capacity of streptavidin. Mixed SAMs prepared from loading solutions containing 75-95% of the biotinylated alkanethiol resulted in high immobilization levels of functional streptavidin. The thin layers of streptavidin subsequently can be used for the immobilization of a broad spectrum of biotinylated biomolecules (e.g. oligonucleotides, cDNA, peptides, proteins, antibodies, and carbohydrates) and provides therefore an excellent platform for the fabrication of chips/arrays for biosensor and screening applications. This is successfully demonstrated by monitoring the hybridization between a biotinylated 24-mer capturing oligonucleotide and a labeled target 89-mer DNA using a fluorescence-based DNA-microarray detection system. Moreover, the DNA-microarray experiments also revealed (i) good selectivity when comparing the response of the complementary oligonucleotide with that of a random 24-mer capturing oligonucleotide and (ii) low levels of nonspecific binding to the streptavidin surface.
|
|
| 20. |
- Skyttner, Camilla, 1985-
(författare)
-
Peptide-Liposome Model Systems for Triggered Release
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Liposomes are widely used in drug delivery to improve drug efficacy and to reduce side effects. For liposome-encapsulated drugs to become bioavailable and provide a therapeutic effect they must be released, which typically is a slow process that primarily relies on passive diffusion, liposome rupture or endocytotic uptake. Achieving drug concentrations within the therapeutic window can thus be challenging, resulting in poor efficacy and higher risks drug resistance. Finding means to modulate lipid membrane integrity and to trigger rapid and efficient release of liposomal cargo is thus critical to improve current and future liposomal drug delivery systems. The possibilities to tailor lipid composition and surface functionalization is vital for drug delivery applications but also make liposomes attractive model systems for studies of membrane active biomolecules.The overall aim of this thesis work has been to develop new strategies for triggering and controlling changes in lipid membrane integrity and to study the interactions of membrane active peptides with model lipid membranes using both de novo designed and biologically derived synthetic amphipathic cationic peptides. Two different sets of designed peptides have been explored that can fold and heterodimerize into a coiled coil and helix-loop-helix fourhelix bundle, respectively. Conjugation of the cationic lysine rich peptides to liposomes triggered a rapid and concentration dependent release. The additions of their corresponding glutamic acid-rich complementary peptides inhibited the release of liposomal cargo. Possibilities to reduce the inhibitory effect by both proteolytic digestion of the inhibitory peptide and by means of heterodimer exchange have been investigated. Moreover, the effects of peptide size and composition and ability to fold have been studied in order to elucidate the factors that influence the membrane permeabilizing effects of the peptides.In addition, the membrane activity of a the two-peptide bacteriocin PLNC8α and PLNC8β has been explored using liposomes as a model system. PLNC8αβ are expressed by Lactobacillus plantarum and were shown to display pronounced membrane-partition folding coupling, leading to rapid release of liposome encapsulated carboxyfluorescein. PLNC8αβ also kill and suppressed growth of the gram-negative bacteria Porphyromonas gingivalis by efficiently damaging the bacterial membrane.Although membrane active peptides are highly efficient in perturbing lipid membrane integrity, possibilities to trigger release using external stimuli are also of large interest for therapeutic applications. Light-induced heating of liposome encapsulated gold nanoparticles (AuNPs) has been shown by others as a potential strategy to trigger drug release. To facilitate fabrication of thermoplasmonic liposome systems we developed a simple method for synthesis of small AuNPs inside liposomes, using the liposomes as nanoscale reaction vessels.The work presented in this thesis provides new knowledge and techniques for future development of liposome-based drug delivery systems, peptide-based therapeutics and increase our understanding of peptide-lipid interactions.
|
|
| 21. |
- Utterström, Johanna, 1993-
(författare)
-
Design and Optimization of Membrane Active Peptides and Lipid Vesicles for Triggered Release
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Liposomes can reduce toxic side effects and improve the efficacy of drugs and several liposome-based drug formulations are approved for clinical use. The therapeutic effect is dependent on the bioavailability of the drug and a slow drug release from liposomes can reduce their efficacy. Multiple strategies have been proposed to control the release of drugs from liposomes using both external stimuli such as light, heat and ultrasound, and endogenous factors such as changes in pH or enzymatic activity. However, because of the difficulties to efficiently modulate lipid membrane permeability and the challenges to trigger drug release in the target tissue, no stimuli responsive liposomes have so far been approved. There is consequently a great need for new means to tune lipid membrane integrity for liposome cargo release to improve the development of new advanced drug delivery systems for better and safer treatment of patients. The aim of this thesis was to design and explore synthetic membrane active peptides for triggered release from liposomes and to expand the knowledge on how peptide-lipid conjugation strategies and lipid properties affect the membrane activity of the peptides. This work was based on two different de novo designed cationic and amphipathic, conjugation-dependent membrane active peptides (CKV4 and JR2KC). Both peptides fold and adopt α-helical structures upon conjugation to liposomes, triggering lipid membrane destabilization. Addition of cholesterol in the lipid membrane greatly enhanced the release efficiency of JR2KC due to a peptide-triggered lipid phase separation, resulting in domains with high local peptide concentrations. Additionally, both peptide surface concentrations and lipid net charge were found to be important factors for efficient release. However, when the zeta potential decreased below -75 mV, conjugation-independent release mechanisms were triggered. Liposome size was shown to only have minor effects on the release kinetics for both sets of peptides while a mixture of saturated and unsaturated lipids was beneficial for the peptide-triggered membrane destabilization, possibly due to increased propensity for lipid phase separation. In addition to changing lipid properties, peptide-lipid conjugation strategies proved to highly affect the release kinetics, where the Michael addition reaction between a cysteine in the peptide and maleimide-lipids was much more efficient in causing peptide-triggered membrane destabilization than strain-promoted alkyne azide cycloaddition reactions using azide-modified peptides and DBCO-functionalized lipids. However, thiols tend to oxidize under ambient conditions which complicates peptide-lipid conjugation. This was addressed by synthesizing a peptide with a cysteine modified with an enzyme labile thiol protection group. Enzymatic deprotection allowed efficient peptide-lipid conjugation, reducing the risk of peptide oxidation. To further find means to tailor peptide-lipid interactions, we explored the effect of a competing peptide heterodimerization process on lipid membrane destabilization. Addition of a charge complementary peptide to CKV4 resulted in heterodimerization and folding into a coiled coil, which inhibited its membrane activity. However, when the two peptides were synthesized as a single sequence, the membrane activity was altered, most likely due to the induced preorganization increasing membrane affinity. The results presented in this thesis provide new understandings of the complex peptide-lipid interactions that govern peptide-induced release from liposomes and will facilitate further optimization in peptide design for the future development of advanced liposome-based drug delivery systems.
|
|
