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1349 KiB

Open AccessArticle

Synthesis of S-Layer Conjugates and Evaluation of Their Modifiability as a Tool for the Functionalization and Patterning of Technical Surfaces

by Ulrike Weinert, Katrin Pollmann, Astrid Barkleit, Manja Vogel, Tobias Günther and Johannes Raff

Molecules 2015, 20(6), 9847-9861; https://doi.org/10.3390/molecules20069847 - 27 May 2015

Cited by 5 | Viewed by 5408

Abstract

Chemical functional groups of surface layer (S-layer) proteins were chemically modified in order to evaluate the potential of S-layer proteins for the introduction of functional molecules. S-layer proteins are structure proteins that self-assemble into regular arrays on surfaces. One general feature of S-layer [...] Read more.

Chemical functional groups of surface layer (S-layer) proteins were chemically modified in order to evaluate the potential of S-layer proteins for the introduction of functional molecules. S-layer proteins are structure proteins that self-assemble into regular arrays on surfaces. One general feature of S-layer proteins is their high amount of carboxylic and amino groups. These groups are potential targets for linking functional molecules, thus producing reactive surfaces. In this work, these groups were conjugated with the amino acid tryptophan. In another approach, SH-groups were chemically inserted in order to extend the spectrum of modifiable groups. The amount of modifiable carboxylic groups was further evaluated by potentiometric titration in order to evaluate the potential efficiency of S-layer proteins to work as matrix for bioconjugations. The results proved that S-layer proteins can work as effective matrices for the conjugation of different molecules. The advantage of using chemical modification methods over genetic methods lies in its versatile usage enabling the attachment of biomolecules, as well as fluorescent dyes and inorganic molecules. Together with their self-assembling properties, S-layer proteins are suitable as targets for bioconjugates, thus enabling a nanostructuring and bio-functionalization of surfaces, which can be used for different applications like biosensors, filter materials, or (bio)catalytic surfaces. Full article

(This article belongs to the Special Issue Bioconjugations)

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1686 KiB

Open AccessCommunication

Site-Specific Bioconjugation of an Organometallic Electron Mediator to an Enzyme with Retained Photocatalytic Cofactor Regenerating Capacity and Enzymatic Activity

by Sung In Lim, Sungho Yoon, Yong Hwan Kim and Inchan Kwon

Molecules 2015, 20(4), 5975-5986; https://doi.org/10.3390/molecules20045975 - 07 Apr 2015

Cited by 10 | Viewed by 6854

Abstract

Photosynthesis consists of a series of reactions catalyzed by redox enzymes to synthesize carbohydrates using solar energy. In order to take the advantage of solar energy, many researchers have investigated artificial photosynthesis systems mimicking the natural photosynthetic enzymatic redox reactions. These redox reactions [...] Read more.

Photosynthesis consists of a series of reactions catalyzed by redox enzymes to synthesize carbohydrates using solar energy. In order to take the advantage of solar energy, many researchers have investigated artificial photosynthesis systems mimicking the natural photosynthetic enzymatic redox reactions. These redox reactions usually require cofactors, which due to their high cost become a key issue when constructing an artificial photosynthesis system. Combining a photosensitizer and an Rh-based electron mediator (RhM) has been shown to photocatalytically regenerate cofactors. However, maintaining the high concentration of cofactors available for efficient enzymatic reactions requires a high concentration of the expensive RhM; making this process cost prohibitive. We hypothesized that conjugation of an electron mediator to a redox enzyme will reduce the amount of electron mediators necessary for efficient enzymatic reactions. This is due to photocatalytically regenerated NAD(P)H being readily available to a redox enzyme, when the local NAD(P)H concentration near the enzyme becomes higher. However, conventional random conjugation of RhM to a redox enzyme will likely lead to a substantial loss of cofactor regenerating capacity and enzymatic activity. In order to avoid this issue, we investigated whether bioconjugation of RhM to a permissive site of a redox enzyme retains cofactor regenerating capacity and enzymatic activity. As a model system, a RhM was conjugated to a redox enzyme, formate dehydrogenase obtained from Thiobacillus sp. KNK65MA (TsFDH). A RhM-containing azide group was site-specifically conjugated to p-azidophenylalanine introduced to a permissive site of TsFDH via a bioorthogonal strain-promoted azide-alkyne cycloaddition and an appropriate linker. The TsFDH-RhM conjugate exhibited retained cofactor regenerating capacity and enzymatic activity. Full article

(This article belongs to the Special Issue Bioconjugations)

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1095 KiB

Open AccessArticle

A Facile Route to Tailoring Peptide-Stabilized Gold Nanoparticles Using Glutathione as a Synthon

by Rosina Ho Wu, Tan P. Nguyen, Grant W. Marquart, Thomas J. Miesen, Theresa Mau and Marilyn R. Mackiewicz

Molecules 2014, 19(5), 6754-6775; https://doi.org/10.3390/molecules19056754 - 23 May 2014

Cited by 29 | Viewed by 12051

Abstract

The preparation of gold nanoparticles (AuNPs) of high purity and stability remains a major challenge for biological applications. This paper reports a simple synthetic strategy to prepare water-soluble peptide-stabilized AuNPs. Reduced glutathione, a natural tripeptide, was used as a synthon for the growth [...] Read more.

The preparation of gold nanoparticles (AuNPs) of high purity and stability remains a major challenge for biological applications. This paper reports a simple synthetic strategy to prepare water-soluble peptide-stabilized AuNPs. Reduced glutathione, a natural tripeptide, was used as a synthon for the growth of two peptide chains directly on the AuNP surface. Both nonpolar (tryptophan and methionine) and polar basic (histidine and dansylated arginine) amino acids were conjugated to the GSH-capped AuNPs. Ultracentrifugation concentrators with polyethersulfone (PES) membranes were used to purify precursor materials in each stage of the multi-step synthesis to minimize side reactions. Thin layer chromatography, transmission electron microscopy, UV-Visible, ¹H-NMR, and fluorescence spectroscopies demonstrated that ultracentrifugation produces high purity AuNPs, with narrow polydispersity, and minimal aggregation. More importantly, it allows for more control over the composition of the final ligand structure. Studies under conditions of varying pH and ionic strength revealed that peptide length, charge, and hydrophobicity influence the stability as well as solubility of the peptide-capped AuNPs. The synthetic and purification strategies used provide a facile route for developing a library of tailored biocompatible peptide-stabilized AuNPs for biomedical applications. Full article

(This article belongs to the Special Issue Bioconjugations)

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306 KiB

Open AccessCommunication

Development of Multi-Functional Chelators Based on Sarcophagine Cages

by Shuanglong Liu, Zibo Li and Peter S. Conti

Molecules 2014, 19(4), 4246-4255; https://doi.org/10.3390/molecules19044246 - 03 Apr 2014

Cited by 17 | Viewed by 6660

Abstract

A new class of multifunctionalized sarcophagine derivatives was synthesized for ⁶⁴Cu chelation. The platform developed in this study could have broad applications in ⁶⁴Cu-radiopharmaceuticals. Full article

(This article belongs to the Special Issue Bioconjugations)

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346 KiB

Open AccessArticle

Synthesis of PNA Oligoether Conjugates

by Alice Ghidini, Peter Steunenberg, Merita Murtola and Roger Strömberg

Molecules 2014, 19(3), 3135-3148; https://doi.org/10.3390/molecules19033135 - 13 Mar 2014

Cited by 3 | Viewed by 7540

Abstract

Several different approaches have been explored for conjugation of oligoethers to PNA with internally or N-terminal placed diaminopropionic acid residues. Single and double conjugation of 2-(2-(2-aminoethoxy)ethoxy)ethanol was obtained using carbonyldimidazole. Using a post PNA-assembly coupling procedure the building block 2-(2-(2-(benzoyloxy)ethoxy)ethoxy)acetic acid multiple attachment [...] Read more.

Several different approaches have been explored for conjugation of oligoethers to PNA with internally or N-terminal placed diaminopropionic acid residues. Single and double conjugation of 2-(2-(2-aminoethoxy)ethoxy)ethanol was obtained using carbonyldimidazole. Using a post PNA-assembly coupling procedure the building block 2-(2-(2-(benzoyloxy)ethoxy)ethoxy)acetic acid multiple attachment of 2-(2-(2-hydroxyethoxy)ethoxy)acetyl groups to both N-terminal and β-amino groups of inserted diaminopropionic acids residues was achieved. Use of a new oligoether functionalized amino acid allows inclusion of oligoether conjugates during on-line machine assisted synthesis which also allowed combination of methods for attachment of different oligoethers and co-conjugation of neocuproine as well as conjugation of an aminosugar. Full article

(This article belongs to the Special Issue Bioconjugations)

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Review

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382 KiB

Open AccessReview

Exploiting Protected Maleimides to Modify Oligonucleotides, Peptides and Peptide Nucleic Acids

by Clément Paris, Omar Brun, Enrique Pedroso and Anna Grandas

Molecules 2015, 20(4), 6389-6408; https://doi.org/10.3390/molecules20046389 - 10 Apr 2015

Cited by 20 | Viewed by 11112

Abstract

This manuscript reviews the possibilities offered by 2,5-dimethylfuran-protected maleimides. Suitably derivatized building blocks incorporating the exo Diels-Alder cycloadduct can be introduced at any position of oligonucleotides, peptide nucleic acids, peptides and peptoids, making use of standard solid-phase procedures. Maleimide deprotection takes place upon [...] Read more.

This manuscript reviews the possibilities offered by 2,5-dimethylfuran-protected maleimides. Suitably derivatized building blocks incorporating the exo Diels-Alder cycloadduct can be introduced at any position of oligonucleotides, peptide nucleic acids, peptides and peptoids, making use of standard solid-phase procedures. Maleimide deprotection takes place upon heating, which can be followed by either Michael-type or Diels-Alder click conjugation reactions. However, the one-pot procedure in which maleimide deprotection and conjugation are simultaneously carried out provides the target conjugate more quickly and, more importantly, in better yield. This procedure is compatible with conjugates involving oligonucleotides, peptides and peptide nucleic acids. A variety of cyclic peptides and oligonucleotides can be obtained from peptide and oligonucleotide precursors incorporating protected maleimides and thiols. Full article

(This article belongs to the Special Issue Bioconjugations)

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1053 KiB

Open AccessReview

Development of Bioorthogonal Reactions and Their Applications in Bioconjugation

by Mengmeng Zheng, Li Zheng, Peiyuan Zhang, Jinbo Li and Yan Zhang

Molecules 2015, 20(2), 3190-3205; https://doi.org/10.3390/molecules20023190 - 16 Feb 2015

Cited by 41 | Viewed by 12810

Abstract

Biomolecule labeling using chemical probes with specific biological activities has played important roles for the elucidation of complicated biological processes. Selective bioconjugation strategies are highly-demanded in the construction of various small-molecule probes to explore complex biological systems. Bioorthogonal reactions that undergo fast and [...] Read more.

Biomolecule labeling using chemical probes with specific biological activities has played important roles for the elucidation of complicated biological processes. Selective bioconjugation strategies are highly-demanded in the construction of various small-molecule probes to explore complex biological systems. Bioorthogonal reactions that undergo fast and selective ligation under bio-compatible conditions have found diverse applications in the development of new bioconjugation strategies. The development of new bioorthogonal reactions in the past decade has been summarized with comments on their potentials as bioconjugation method in the construction of various biological probes for investigating their target biomolecules. For the applications of bioorthogonal reactions in the site-selective biomolecule conjugation, examples have been presented on the bioconjugation of protein, glycan, nucleic acids and lipids. Full article

(This article belongs to the Special Issue Bioconjugations)

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583 KiB

Open AccessReview

Hyaluronic Acid Conjugates as Vectors for the Active Targeting of Drugs, Genes and Nanocomposites in Cancer Treatment

by Silvia Arpicco, Paola Milla, Barbara Stella and Franco Dosio

Molecules 2014, 19(3), 3193-3230; https://doi.org/10.3390/molecules19033193 - 17 Mar 2014

Cited by 104 | Viewed by 14374

Abstract

Hyaluronic acid (HA) is a naturally-occurring glycosaminoglycan and a major component of the extracellular matrix. Low levels of the hyaluronic acid receptor CD44 are found on the surface of epithelial, hematopoietic, and neuronal cells; it is overexpressed in many cancer cells, and in [...] Read more.

Hyaluronic acid (HA) is a naturally-occurring glycosaminoglycan and a major component of the extracellular matrix. Low levels of the hyaluronic acid receptor CD44 are found on the surface of epithelial, hematopoietic, and neuronal cells; it is overexpressed in many cancer cells, and in particular in tumor-initiating cells. HA has recently attracted considerable interest in the field of developing drug delivery systems, having been used, as such or encapsulated in different types of nanoassembly, as ligand to prepare nano-platforms for actively targeting drugs, genes, and diagnostic agents. This review describes recent progress made with the several chemical strategies adopted to synthesize conjugates and prepare novel delivery systems with improved behaviors. Full article

(This article belongs to the Special Issue Bioconjugations)

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