Biomedical subjects

Jörg Ackermann

Publications and source records attributed to Jörg Ackermann.

4 recordsLinked to original sources

PubMed2005

Alpha,omega-distyryl oligothiophenes: high mobility semiconductors for environmentally stable organic thin film transistors.

Critical to the development of organic electronics is the design and synthesis of new organic semiconductors with improved electrical performance and enhanced environmental stability. We present in this communication the synthesis of a series of simple oligothiophene derivatives that bear the styryl unit as terminal substituent. Thin film field-effect transistors incorporating these compounds show high electrical performance, such as mobilities as high as 0.1 cm2/Vs, along with exceptional stability under ambient conditions. Especially, the longer oligomer, DS-4T, containing the quaterthiophene core gives rise to devices that show no decrease in performance after more than 17 months of storage and under continuous operation. Such stability features are unprecedented in the oligothiophene series.

Journal Article↗

PubMed2005

Optimization and design of oligonucleotide setup for strand displacement amplification.

Several advantages of strand displacement amplification (SDA) as an all-purpose DNA amplification reaction are due to it isothermal mechanism. The major problem of isothermal amplification mechanism is the accumulation of non-predictable byproduct especially for longer incubation time and low concentrations of initial template DNA. New theoretical strategies to tackle the difficulties regarding the specificity of the reaction are experimentally verified. Besides improving the reaction conditions, the stringency of primer hybridization can be distinctly improved by computer based sequence prediction algorithms based on the thermodynamic stability of DNA hybrid a described by the partition function of the hybridization reaction. An alternative SDA mechanism, with sequences developed by this means is also investigated.

Algorithms↗

PubMed2005

Design of organic semiconductors: tuning the electronic properties of pi-conjugated oligothiophenes with the 3,4-ethylenedioxythiophene (EDOT) building block.

Hybrid oligothiophenes based on a various combinations of thiophene and 3,4-ethylenedioxythiophene (EDOT) groups have been synthesized. UV/Vis absorption spectra show that the number and relative positions of the EDOT groups considerably affect the width of the HOMO-LUMO gap and the rigidity of the conjugated system. Analysis of the crystallographic structure of two hybrid quaterthiophenes confirms that insertion of two adjacent EDOT units in the middle of the molecule leads to a self-rigidification of the conjugated systems by intramolecular SO interactions. Cyclic voltammetry data shows that the first oxidation potential of the oligomers decreases with increasing chain length and increasing number of EDOT groups for a given chain length. Electrochemical studies and theoretical calculations show that the positions of the EDOT units in the conjugated chain control the potential difference (DeltaE(p)) between the first and second oxidation steps. Moving the EDOT groups from the outer to the inner positions of the conjugated system increases DeltaE(p). Theoretical calculations confirm that this phenomenon reflects an increase of the intramolecular coulombic repulsion between positive charges in the dication. A thin-film field-effect transistor was fabricated by vacuum sublimation of a pentamer with alternating thiophene-EDOT structure, and the hole mobility was determined.

Bridged Bicyclo Compounds, Heterocyclic↗

PubMed2003

DNA library design for molecular computation.

A novel approach to designing a DNA library for molecular computation is presented. The method is employed for encoding binary information in DNA molecules. It aims to achieve a practical discrimination between perfectly matched DNA oligomers and those with mismatches in a large pool of different molecules. The approach takes into account the ability of DNA strands to hybridize in complex structures like hairpins, internal loops, or bulge loops and computes the stability of the hybrids formed based on thermodynamic data. A dynamic programming algorithm is applied to calculate the partition function for the ensemble of structures, which play a role in the hybridization reaction. The applicability of the method is demonstrated by the design of a twelve-bit DNA library. The library is constructed and experimentally tested using molecular biology tools. The results show a high level of specific hybridization achieved for all library words under identical conditions. The method is also applicable for the design of primers for PCR, DNA sequences for isothermal amplification reactions, and capture probes in DNA-chip arrays. The library could be applied for integrated DNA computing of twelve-bit instances of NP-complete combinatorial problems by multi-step DNA selection in microflow reactors.

Algorithms↗