Katharina Linkert

λ‐Orthogonal Pericyclic Macromolecular Photoligation

A photochemical strategy enabling λ-orthogonal reactions is introduced to construct macromolecular architectures and to encode variable functional groups with site-selective precision into a single molecule by the choice of wavelength. λ-Orthogonal pericyclic reactions proceed independently of one another by the selection of functional groups that absorb light of specific wavelengths. The power of the new concept is shown by a one-pot reaction of equimolar quantities of maleimide with two polymers carrying different maleimide-reactive endgroups, that is, a photoactive diene (photoenol) and a nitrile imine (tetrazole). Under selective irradiation at λ=310-350 nm, any maleimide (or activated ene) end-capped compound reacts exclusively with the photoenol functional polymer. After complete conversion of the photoenol, subsequent irradiation at λ=270-310 nm activates the reaction of the tetrazole group with functional enes. The versatility of the approach is shown by λ-orthogonal click reactions of complex maleimides, functional enes, and polymers to the central polymer scaffold.

Spatially controlled photochemical peptide and polymer conjugation on biosurfaces

An efficient phototriggered Diels-Alder conjugation is utilized to graft in an effective and straightforward approach poly(trifluoro ethyl methacrylate) (Mn = 3700 Da, Đ = 1.27) and a model peptide (GIGKFLHS) onto thin hyaluronan films and cellulose surfaces. The surfaces were functionalized with an o-quinodimethane moiety - capable of releasing a caged diene - via carbodiimide mediated coupling. The o-quinodimethane group is employed as a photoactive linker to tether predefined peptide/polymer strands in a spatially controlled manner onto the biosurface by photoenol ligation. An in-depth characterization employing XPS, ToF-SIMS, SPR, ellipsometry, and AFM was conducted to evidence the effectiveness of the presented approach.

Spatially Controlled Surface Immobilization of Nonmodified Peptides

A phencyclone derivative is used to achieve light-controlled immobilization of peptides possessing only natural amino acids. The photoactive precursor (blue in picture) is formed in a Diels-Alder reaction and can undergo light-triggered ring-opening reactions with amines. Successful surface patterning with a genuine c(RGDfK) peptide (green) is evidenced by imaging time-of-flight secondary-ion mass spectrometry (ToF-SIMS). Copyright

Ambient temperature ligation of diene functional polymer and peptide strands onto cellulose via photochemical and thermal protocols.

In the present contribution, two novel ambient temperature avenues are introduced to functionalize solid cellulose substrates in a modular fashion with synthetic polymer strands (poly(trifluoro ethyl methacrylate), PTFEMA, Mn = 4400 g mol(-1) , Đ = 1.18) and an Arg-Gly-Asp (RGD) containing peptide sequence. Both protocols rely on a hetero Diels-Alder reaction between an activated thiocarbonyl functionality and a diene species. In the first-thermally activated-protocol, the cellulose features surface-expressed thiocarbonylthio compounds, which readily react with diene terminal macromolecules at ambient temperature. In the second protocol, the reactive ene species are photochemically generated based on a phenacyl sulfide-decorated cellulose surface, which upon irradiation expresses highly reactive thioaldehyde species. The generated functional hybrid surfaces are characterized in-depth via ToF-SIMS and XPS analysis, revealing the successful covalent attachment of the grafted materials, including the spatially resolved patterning of both synthetic polymers and peptide strands using the photochemical protocol. The study thus provides a versatile platform technology for solid cellulose substrate modification via efficient thermal and photochemical ligation strategies.

Gaining insights into specific drug formulation additives for solubilizing a potential Anti-Alzheimer disease drug B4A1

The pharmacological profiles of small molecule drugs are often challenged by their poor water solubility. Sequence-defined peptides attached to poly(ethylene glycol) (PEG) offer opportunities to overcome these difficulties by acting as drug-specific formulation additives. The peptide-PEG conjugates enable specific, noncovalent drug binding via tailored peptide/drug interactions as well as provide water solubility and drug shielding by well-solvated PEG-blocks. A systematic set of specific solubilizers for B4A1 as a potential anti-Alzheimer disease drug is synthesized and variations involve the length of the PEG-blocks as well as the sequences of the peptidic drug-binding domain. The solubilizer/B4A1 complexes are studied in order to understand contributions of both PEG and peptide segments on drug payload capacities, drug/carrier aggregate sizes, and influences on inhibition of the Tau-protein aggregation in an in vitro assay.