Clickable 5′-γ-Ferrocenyl Adenosine Triphosphate Bioconjugates in Kinase-Catalyzed Phosphorylations
Dr. Nan Wang, Dr. Zhe She, Yen-Chun Lin, Prof. Sanela Martić, Dr. David J. Mann and Prof. Heinz-Bernhard Kraatz
A clickable site has been introduced into a tri-functional 5′-γ-ferrocenyl (Fc) adenosine triphosphate (Fc-ATP) derivative, which has been used as an effective co-substrate for kinase-catalyzed phosphorylation. The compound was also applied to the Fc-Ab1/Ab2 system, providing both electrochemical results and immunodetection. The clickable reaction site makes direct modification possible, which greatly expands its application.
Self-Assembly of Guanosine and Deoxy-Guanosine into Hydrogels: Monovalent Cation Guided Modulation of Gelation, Morphology and Self-Healing Properties
Bimalendu Adhikari, Afzal Shah and Heinz-Bernhard Kraatz
Herein, we report the effect of monovalent cations including Na+, K+, Rb+, Ag+, Au+, Tl+, Hg+ and NH4+ on the stimulation of purine nucleosides guanosine (G) and deoxy-guanosine (dG) to self-assemble into hydrogels. The gelation properties in terms of gel crystallization, lifetime stability, thermo-reversibility, minimum gelation concentration, gel melting temperature, thixotropic property and others were thoroughly investigated and compared not only between two nucleosides but also among different metal ions. A few metal ions were found to induce G/dG to form gels with much improved lifetime stability. The results revealed that dG is a much better gelator than G for introduction of thixotropic property. Interestingly, morphological, fluorescence and rheological (thixotropic) properties of the gels were found to modulate significantly by changing the metal ions. In the presence of K+ ion, G produces self-supporting tight gel but it has poor lifetime stability. In contrast, the presence of K+ ion stimulates dG to form a very loose gel but associated with excellent lifetime stability and thixotropic property. In this context, we have successfully engineered a self-supporting stable co-gel using simple co-gelation method by mixing equimolar amount of K+ induced G and dG gel and this co-gel shows long lifetime stability, self-healing and injectable properties which may allow for a broad range of biological applications. Furthermore, Ag+ induced G gel was exploited for the light triggered in-situ fabrication of uniform AgNPs within gel to make a nano-bio hybrid material.
Redox-Triggered Changes in the Self-Assembly of a Ferrocene-Peptide Conjugate
Bimalendu Adhikari and Heinz-Bernhard Kraatz
Ultrasonication of a ferrocene conjugate of a short amyloid peptide (Aβ18–20) in toluene causes formation of an organogel, which undergoes dramatic structural changes upon oxidation from a nanofibrillar network to spherical micelles. This morphological change is redox-controlled and reversible.
Tailoring zinc porphyrin to the Ag nanostructure substrate: an effective approach for photoelectrochemical studies in the presence of mononucleotides
Farkhondeh Fathi, Cong Kong, Yueqiang Wang, Yongshu Xie, Yi-Tao Long and Heinz-Bernhard Kraatz
The substituted porphyrin 2-cyano-3-(2′-(5′,10′,15′,20-tetraphenyl porphyrinato zinc-(II))yl) acrylic acid was used to modify nanostructured Ag surfaces. This porphyrin-modified surface exhibits photocurrent when exposed to a light source, which is modulated in the presence of nucleotides. The addition of the nucleotides adenosine-5′-monophosphate (AMP), guanosine-5′-monophosphate (GMP) and cytidine-5′-monophosphate (CMP) causes partial quenching of the photoelectrochemical response of the porphyrin. The quenching efficiency is 80%, 68% and 48% for AMP, CMP and GMP, respectively. This work represents a new aspect of Ag NS substrates and highlights their usefulness as transducers a for potential chemosensor systems.
S. Martic, M. Gabriel, J. P. Turowec, D. W. Litchfield, H. B. Kraatz
Protein kinases can use ferrocene-ATP conjugates to transfer the redox active ferrocene group to protein and peptide targets. Ferrocene transfer can be quantified electrochemically with the help of an antiferrocene antibody.
Electrochemical identification of artificial oligonucleotides related to bovine species. Potential for identification of species based on mismatches in the mitochondrial cytochrome C1 oxidase gene
Mohtashim H. Shamsi and Heinz-Bernhard Kraatz
Our studies show that electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) of films of ds-DNA on gold allow us to distinguish between mitochondrial DNA fragments of the cytochrome c1 oxidase (mt-Cox1) of three related species of the subfamily ‘Bovinae’ (Bos taurus, Bison bison, and Bison bonasus). In EIS, a perfectly matched DNA gives rise to a considerably larger charge transfer resistance Rct compared to mismatched pairings. Differences in charge transfer resistance, ΔRct, before and after the addition of Zn2+ ions provide an additional tool for identification. In addition, all ds-DNA films were studied by SECM and their kinetic parameters were determined. Perfectly matched ds-DNAs are readily distinguished from mismatched duplexes by their lower rate constants. Our system can be used multiple times by dehybridization and rehybridization of capture strands up to the 250 pmole level.
Electrochemical probing of HIV enzymes using ferrocene-conjugated peptides on surfaces
Kagan Kerman and Heinz-Bernhard Kraatz
Analyst, 2009, 134, 2400 – 2404
One of the current pathways to develop inhibitors that target different steps in the life cycle of the human immunodeficiency virus (HIV) is blocking the function of the HIV-related proteins such as HIV-1 integrase (HIV-1 IN), HIV-1 reverse transcriptase (HIV-1 RT) and HIV-1 protease (HIV-1 PR), which are essential proteins that control the ability of HIV to infect cells, produce new copies of the virus, or cause disease. We have demonstrated for the first time the detection of these enzymes at nanomolar levels using ferrocene (Fc)-conjugated peptides on gold microelectrodes. The interaction between the Fc-conjugated peptides and the enzymes was studied by cyclic voltammetry. As the protein concentration increased, the electrochemical behaviour of the surface-bound Fc- bioconjugate changed, indicating that HIV protein was binding to the peptide film and encapsulating the Fc redox center on the surface. The electrochemical responses shifted to higher potentials and decreased in the current intensity, as the concentrations of the HIV-1 enzymes increased. The optimization studies were performed by changing the pH and NaCl concentration. Control experiments involved the exposure of the Fc-conjugated peptides with all the enzymes. This general procedure can be readily applied in the future to the multiplexed detection of several HIV-related proteins, as well as the high-throughput screening of candidate inhibitors for AIDS therapy.
Piotr Michal Diakowski and Heinz-Bernhard Kraatz
Probing ds-DNA films in the presence of Zn2+ ions by scanning electrochemical microscopy (SECM) allows the unequivocal detection of a single-nucleotide mismatch and provides information about its position within the duplex.
Heinz-Bernhard Kraatz and Nils Metzler-Nolte
Destined to set the standard, this book meets the need for a didactic textbook focusing on the role of model systems in bioinorganic chemistry. The first part features concepts in bioinorganic chemistry such as electron transfer, medicinal inorganic chemistry, bioorganometallics and metal DNA complexes, while the second part presents inorganic model chemistry on metallo-enzymes, organized by metal ion.
Systematizing structural motifs and nomenclature in 1,n′-disubstituted ferrocene peptides
Srećko I. Kirin, Heinz-Bernhard Kraatz and Nils Metzler-Nolte
Ferrocene peptide conjugates display an array of structural features including helical ferrocene based chirality and a number of different intramolecular hydrogen bonding patterns. In this tutorial review we present a rigorous nomenclature for these systems, followed by a section that summarises and categorises the structures known to date. The issues discussed herein are of general relevance for all metallocene-based chiral transition metal catalysts and peptide turn mimetics.
Date: 06 Nov 2008
Peptide Electron Transfer: More Questions than Answers
Yi-Tao Long, Erfan Abu-Irhayem and Heinz-Bernhard Kraatz
Nature has specifically designed proteins, as opposed to DNA, for electron transfer. There is no doubt about the electron transfer within proteins compared with the uncertain and continuing debate about charge transfer through DNA. However, the exact mechanism of electron transfer within peptide systems has been a source of controversy. Two different mechanisms for electron transfer between a donor and an acceptor, electron hopping and bridge-assisted superexchange, have been proposed, and are supported by experimental evidence and theoretical calculations. Several factors were found to affect the kinetics of this process, including peptide chain length, secondary structure and hydrogen bonding. Electrochemical measurements of surface-supported peptides have contributed significantly to the debate. Here we summarize the current approaches to the study of electron transfer in peptides with a focus on surface measurements and comment on these results in light of the current and often controversial debate on electron transfer mechanisms in peptides.
Date: 24 JUN 2005
Stimuli responsive materials: new avenues toward smart organic devices
Roie Yerushalmi, Avigdor Scherz, Milko E. van der Boom and Heinz-Bernhard Kraatz
“Smart” patternable polymer-based materials that can be designed from various molecular building blocks show great potential, as they may be used in many fields, including nanotechnology, biochemistry, organic and physical chemistry, and materials science. The focus of this highlight will be on the basic design characteristics of practical Stimuli Responsive Materials (SRMs), the wide range of potential applications and the challenges to be accomplished in this rapidly expanding area. In particular, recent developments are described which are related to two of the many fundamental aspects of stimuli triggered responses: those that are photo-triggered and those that are solvent triggered. These selected state-of-the-art examples demonstrate the large scope and diversity in terms of activation mechanism, response time and property control.
Date: 04 Jul 2005