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F Kirpekar

Publications and source records attributed to F Kirpekar.

24 records · Page 2Linked to original sources
PubMed1994

Incorporation of (R)- and (S)-3',4'-seco-thymidine into oligodeoxynucleotides: hybridization properties and enzymatic stability.

Novel flexible oligodeoxynucleotide analogues containing (R)- and (S)-3',4'-seco-thymidine were synthesized on an automated DNA-synthesizer using the phosphoramidite approach. Oligodeoxynucleotide analogues (17-mers) having one or three modifications in the middle or one or two modifications in the ends were evaluated with respect to hybridization properties and enzymatic stability. 3'-End-modified oligomers were stable towards 3'-exonuclease degradation and displayed acceptable hybridization properties.

Base Sequence↗
PubMed1994

A search for an essential function of the replication origin ARS1 in the life cycle of Saccharomyces cerevisiae.

We have investigated the significance of the chromosomal replication origin, ARS1, during the entire life cycle of yeast. This was done by substituting the chromosomal copy with a series of ars1 deletion mutants. It was shown that the ARS1 replication origin is not essential for mitotic or premeiotic DNA replication since no effect on growth, chromosomal loss rate and spore viability was observed in the ars1 mutant strains. We conclude that replication origins are abundantly, present in the yeast genome and that the removal of a single replication origin is compensated for by replication forks emanating from neighbouring origins.

Chromosomes, Fungal↗
PubMed1993

Ion stability of nucleic acids in infrared matrix-assisted laser desorption/ionization mass spectrometry.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) with infrared laser light of a wavelength of 2.94 microns has been used for the analysis of nucleic acids. Spectra of oligodeoxynucleotides up to 26 nucleotides, oligothymidylic acids up to 100 nucleotides as well as different synthetic RNA oligomers and RNA transcripts up to 104 nucleotides are presented. A main problem in the analysis of oligodeoxynucleotides was found to be related to the loss of bases. The stability of oligothymidylic acids as opposed to oligodeoxynucleotides containing all four bases indicates that the loss of bases is correlated with A, C and G protonation which decreases the stability of the N-glycosidic bond. Experiments indicate that the breakage of the N-glycosidic bond probably occurs during the desorption process due to proton transfer from the phosphodiester groups to the ionizable bases. RNA displayed a significantly higher stability in MALDI-MS due to the presence of a 2'-OH group. Consequently, signals of RNA transcripts with a length of up to 142 nucleotides could be detected by MALDI-MS. Technical details of the method, including the distribution of positive counterions on the phosphodiester backbone, the upper mass limit and mass accuracy are discussed along with a number of potential analytical applications.

Base Sequence↗
PubMed1992

Mutational analysis of a variant of ARS1 from Saccharomyces cerevisiae.

A naturally occurring single base-pair G to A transition, creating a 10/11 near-match close to the essential 11 base-pair core consensus of ARS1, was used to investigate the importance of near-match sequences. The 10/11 near-match can not substitute for the core consensus since an ARS- phenotype is observed when the core consensus is deleted. However, deletion mutations revealed that this near-match together with a short palindromic sequence, also situated in the B-flanking region, comprise a single element crucial for optimal ARS function. The palindrome has the potential of forming a stem-loop structure. Rather precise observations concerning the borders of the B-region were achieved. The four base pairs separating the near-match from the core consensus perform a spacing function where the identity of the bases are unimportant. However, this spacing is highly important since deletion of these four base pairs leads to an ARS- phenotype.

Base Sequence↗
PubMedDate not supplied

R-banding and in situ hybridization localization of single copy genes on high resolution banded chromosomes.

A method to preserve high resolution R-bands on human lymphocyte chromosomes after in situ hybridization to 3H-labelled probes and autoradiography is presented. The technique was used to re-examine the location of the known oncogene N-myc. Due to the high resolution power of the present technique, this gene could be located to subband 2p24.1 in the human karyotype.

Chromosome Banding↗