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H Fritzsche

Publications and source records attributed to H Fritzsche.

At least 19 recordsLinked to original sources
PubMed2003

[Clinical usefulness and perspectives of sentinel node biopsy in the management of breast cancer].

INTRODUCTION: In view of its predictive potential, axillary nodal status plays a particularly important role in breast cancer. The concept of sentinel node biopsy (SNB) revealed an accurate method with low postoperative morbidity for staging the axilla in patients with lymph node-negative breast cancer. The aim of this study was to show that SNB alone must have a place in routine clinical work and is reliable after preoperative chemotherapy (PC) and also in patients with multicentric tumors (MC). PATIENTS AND METHOD: Between April 1997 and March 2002, a total of 300 SNBs were performed in patients with uni- or bilateral breast cancer. Of them, 45 who had completed PC and 13 with multicentric lesions underwent SNB followed by axillary dissection. The sentinel nodes (SN) were labelled with a blue dye and radioactive colloids. Median follow-up was 33.6 months (range 8.2-67.0) (StAw 1.4). RESULTS: The detection rate in the learning phase was 81.8% and later 93.5%, independently of the size of the primary tumor. Overall accuracy and negative predictive value of the first 55 patients, after PC and in those with MC came to 97.8% and 96.7%, 97.6%, 95.8% and 100%, respectively. Through focused pathologic examination, staging was improved in 11.3% of patients. A year after the procedure, one patient developed recurrence. Morbidity after SNB alone was significantly lower than after axillary dissection. CONCLUSION: Our experience shows SNB to be reliable and accurate for axillary staging in breast cancer patients. Morbidity after SNB alone was low. Conclusive data on the local recurrence rate are not yet available. Under certain conditions, SNB appears to have future clinical potential, even in patients with PC and MC, which must be confirmed in further multicentric studies. In the meantime, this method has attained definite value in the surgical therapy of breast cancer patients.

Adult↗
PubMed2001

Is sentinel lymph node biopsy reliable and indicated after preoperative chemotherapy in patients with breast carcinoma?

BACKGROUND: Many studies support the concept and accuracy of sentinel lymph node biopsy (SNB) for staging patients with breast carcinoma, which can be performed with low morbidity in lymph node negative patients. Preoperative chemotherapy (PC) plays an important role in the treatment of patients with operable breast carcinoma and is another approach with which to reduce radical surgery in patients with more advanced disease. It is of interest whether the sentinel lymph node accurately represents the axillary status after PC and, thus, whether the sentinel node concept can be applied to both groups. METHODS: Thirty-three patients underwent SNB after chemotherapy and prior to axillary lymph node dissection. RESULTS: The average greatest tumor dimension before chemotherapy (33 mm +/- 2 mm) was significantly larger (P = 0.000) than after therapy (20 mm +/- 3 mm). Histopathologic complete remission was seen in only three patients. One or two sentinel lymph nodes (average, 1.7 lymph nodes) were identified with certainty in 29 of 33 procedures and accurately predicted axillary lymph node status in all of these patients. Breast-conserving surgery was possible in 21 patients (64%), and axillary lymph nodes were involved in 22 patients (67%). CONCLUSIONS: Even after patients undergo PC, SNB seems to be a reliable method for accurate staging of the axilla in those more advanced breast carcinoma. Thus, axillary dissection may be avoided in certain patients. Lymph node involvement seems to be likely in women with suspicious axillary findings before chemotherapy who have no visible sentinel lymph nodes on preoperative lymphosintigraphy and in patients without recurrent tumors. Further investigation of the SNB concept in this patient group should be evaluated in larger studies.

Adult↗
PubMed2001

Binding of bis-linked netropsin derivatives in the parallel-stranded hairpin form to DNA.

Cis-diammine Pt(II)- bridged bis-netropsin and oligomethylene-bridged bis-netropsin in which two monomers are linked in a tail-to-tail manner bind to the DNA oligomer with the sequence 5'-CCTATATCC-3' in a parallel-stranded hairpin form with a stoichiometry 1:1. The difference circular dichroism (CD) spectra characteristic of binding of these ligands in the hairpin form are similar. They differ from CD patterns obtained for binding to the same duplex of another bis-netropsin in which two netropsin moieties were linked in a head-to-tail manner. This reflects the fact that tail-to-tail and head-to-tail bis-netropsins use parallel and antiparallel side-by-side motifs, respectively, for binding to DNA in the hairpin forms. The binding affinity of cis-diammine Pt(II)-bridged bis-netropsin in the hairpin form to DNA oligomers with nucleotide sequences 5'-CCTATATCC-3' (I), 5'-CCTTAATCC-3' (II), 5'-CCTTATTCC-3' (III), 5'-CCTTTTTCC-3' (IV) and 5'-CCAATTTCC-3' (V) decreases in the order I = II > III > IV > V . The binding of oligomethylene-bridged bis-netropsin in the hairpin form follows a similar hierarchy. An opposite order of sequence preferences is observed for partially bonded monodentate binding mode of the synthetic ligand.

Binding Sites↗
PubMed2001

Solution structure of the dodecamer d-(CATGGGCC-CATG)2 is B-DNA. Experimental and molecular dynamics study.

The DNA duplex d-(CATGGGCCCATG)2 has been studied in solution by FTIR, NMR and CD. The experimental approaches have been complemented by series of large-scale unrestrained molecular dynamics simulation with explicit inclusion of solvent and counterions. Typical proton-proton distances extracted from the NMR spectra and the CD spectra are completely in agreement with slightly modified B-DNA. By molecular dynamics simulation, starting from A-type sugar pucker, a spontaneous repuckering to B-type sugar pucker was observed. Both experimental and theoretical approaches suggest for the dodecamer d-(CATGGGCCCATG)2 under solution conditions puckering of all 2'-deoxyribose residues in the south conformation (mostly C2'-endo) and can exclude significant population of sugars in the north conformation (C3'-endo). NMR, FTIR and CD data are in agreement with a B-form of the dodecamer in solution. Furthermore, the duplex shows a cooperative B-A transition in solution induced by addition of trifluorethanol. This contrasts a recently published crystal structure of the same oligonucleotide found as an intermediate between B- and A-DNA where 23 out of 24 sugar residues were reported to adopt the north (N-type) conformation (C3'-endo) like in A-DNA (Ng, H. L., Kopka, M. L. and Dickerson, R. E., Proc. Natl. Acad. Sci. U S A 97, 2035-2039 (2000)). The simulated structures resemble standard B-DNA. They nevertheless show a moderate shift towards A-type stacking similar to that seen in the crystal, despite the striking difference in sugar puckers between the MD and X-ray structures. This is in agreement with preceding MD reports noticing special stacking features of G-tracts exhibiting a tendency towards the A-type stacking supported by the CD spectra also reflecting the G-tract stacking. MD simulations reveal several noticeable local conformational variations, such as redistribution of helical twist and base pair roll between the central GpC steps and the adjacent G-tract segments, as well as a substantial helical twist variability in the CpA(TpG) steps combined with a large positive base pair roll. These local variations are rather different from those seen in the crystal.

Base Sequence↗
PubMed2001

Low frequency rTMS as an add-on antidepressive strategy: heterogeneous impact on 99mTc-HMPAO and 18 F-FDG uptake as measured simultaneously with the double isotope SPECT technique. Pilot study.

Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are examination procedures that have shown that repetitive transcranial magnetic stimulation (rTMS) is biologically active. The aim of the present study was to investigate the patterns of regional cerebral 18F-fluorodeoxyglucose (18F-FDG) uptake and regional 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) uptake simultaneously during a series of therapeutic rTMS at low frequency. Four drug-resistant depressed patients underwent 10 rTMS as an add-on measure over 14 days. One day before and one day after TMS, simultaneous measurements of 18F-FDG, representing regional cerebral metabolic rate (rCMR), and 99mTc-HMPAO, representing regional cerebral blood flow (rCBF), were carried out. A conventional double head SPECT camera with 511 keV collimators was used. Statistically significant simultaneous overall changes of rCBF and rCMR were found in the upper prefrontal regions bilaterally in terms of increased uptake rates and in the left gyrus frontalis inferior in terms of decreased uptake rates of both isotopes compared to controls. Although this method improves our understanding of rTMS mechanism, there are limitations due to the lower resolution provided. Therapeutic rTMS seems to influence distinct, cortical regions affecting rCBF and rCMR.

Adult↗
PubMed2000

Preliminary findings of simultaneous 18F-FDG and 99mTc-HMPAO SPECT in patients with depressive disorders at rest: differential correlates with ratings of anxiety.

The assumption of a dynamic coupling between regional cerebral blood flow (rCBF) and cerebral glucose metabolic rates (rCMRGlu) has been challenged by simultaneous measurements of both. Through the use of a dual-headed gamma camera with a 511-keV collimator applying the double isotope 18F-FDG and 99mTc-HMPAO SPECT technique, the uptake rates of these isotopes can be semi-quantitatively evaluated. Sixteen depressed patients, diagnosed by ICD-10 criteria and assessed with the 17-item Hamilton Rating Scale for Depression (HRSD), were studied. Based on the severity of HRSD-rated anxiety (item 10: low=1-21; high=3-4), two eight-patient subgroups were formed and compared with 12 age- and handedness-matched healthy control subjects. As regions of interest, we selected areas implicated in the neuroanatomy of anxiety and depression: hippocampus (hippo), basal ganglia (BG) and gyri temporales superiores (G.t.s.). In the control subjects, a significant statistical coupling between rCBF and rCMRGlu was revealed by the Spearman correlation coefficient only in left hippo and left BG. Patients in the low-anxiety subgroup demonstrated a marked dynamic coupling bilaterally for the G.t.s., while patients in the high-anxiety subgroup showed a significant statistical correlation of rCBF and rCMRGlu only in the left G.t.s. These findings indicate that a dynamic coupling between blood flow and glucose metabolism exists only in distinct brain regions, and that the depressive illness has an uncoupling effect on this correlation in the left BG. Furthermore, our results suggest that the HRSD anxiety score might interact with the underlying depressive illness to influence the relationship of rCBF and rCMRGlu.

Adult↗
PubMed1999

Solution structure of a five-adenine bulge loop within a DNA duplex.

The three-dimensional solution structure of a DNA molecule of the sequence 5'-d(GCATCGAAAAAGCTACG)-3' paired with 5'-d(CGTAGCCGATGC)-3' containing a five-adenine bulge loop (dA(5)-bulge) between two double helical stems was determined by 2D (1)H and (31)P NMR, infrared, and Raman spectroscopy. The DNA in both stems adopt a classical B-form double helical structure with Watson-Crick base pairing and C2'-endo sugar conformation. In addition, the two dG/dC base pairs framing the dA(5)-bulge loop are formed and are stable at least up to 30 degrees C. The five adenine bases of the bulge loop are localized at intrahelical positions within the double helical stems. Stacking on the double helical stem is continued for the first four 5'-adenines in the bulge loop. The total rise (the height) of these four stacked adenines roughly equals the diameter of the double helical stem. The stacking interactions are broken between the last of these four 5'-adenines and the fifth loop adenine at the 3'-end. This 3'-adenine partially stacks on the other stem. The angle between the base planes of the two nonstacking adenines (A10 and A11) in the bulge loop reflects the kinking angle of the global DNA structure. The neighboring cytosines opposite the dA(5)-bulge (being parts of the bulge flanking base pairs) do not stack on one another. This disruption of stacking is characterized by a partial shearing of these bases, such that certain sequential NOEs for this base step are preserved. In the base step opposite the loop, an extraordinary hydrogen bond is observed between the phosphate backbone of the 5'-dC and the amino proton of the 3'-dC in about two-thirds of the conformers. This hydrogen bond probably contributes to stabilizing the global DNA structure. The dA(5)-bulge induces a local kink into the DNA molecule of about 73 degrees (+/-11 degrees ). This kinking angle and the mutual orientation of the two double helical stems agree well with results from fluorescence resonance energy transfer measurements of single- and double-bulge DNA molecules.

Adenine↗
PubMed1999

Revascularization of residual viable myocardium improves left ventricular dysfunction in patients after myocardial infarction.

The symptoms and prognosis of patients after myocardial infarction are essentially influenced by left ventricular function. About 50% of infarct related segments contain partly viable myocardium. The aim of this study was to test the hypothesis that regional and global left ventricular function can be improved by revascularization of infarct related segments with residual myocardial viability. In 15 of 30 consecutive patients, residual viable myocardium was found in the affected segment within 2.2 +/- 1.6 months after AMI. Myocardial viability was estimated by exercise-redistribution-reinjection thallium scintigraphy (SPECT imaging). Rest and exercise radionuclide ventriculography was performed to measure regional and global left ventricular ejection fraction before and after revascularization of the infarct related artery. 10 +/- 3 months after revascularization we observed a significant increase in the regional left ventricular ejection fraction at rest (from 32 +/- 16% to 41 +/- 19%; p = 0.03), global left ventricular ejection fraction at rest (from 38 +/- 12% to 46 +/- 11%; p = 0.01), regional LV ejection fraction during exercise (from 34 +/- 16% to 46 +/- 20%; p = 0.01), and global left ventricular ejection fraction during exercise (from 38 +/- 14% to 49 +/- 14%; p = 0.02). The results show that after revascularization of infarct related segments with residual myocardial viability, the regional and global left ventricular ejection fraction may be significantly improved, both at rest and during exercise. Thus infarct related segments should be tested for residual viability. In its presence revascularization is recommended, as the left ventricular function may be markedly improved.

Aged↗
PubMed1999

[Sentinel node biopsy in breast cancer--a minimally invasive procedure for staging of the axilla].

Clinical examinations and imaging methods are not sufficiently reliable for an exact staging of axillary nodes in breast cancer. The sentinel node biopsy concept is a minimally invasive procedure to locate and remove the first and important nodes responsible for draining a tumor. Histologic examinations using immunohistochemical methods permit more accurate staging than hematoxylin and eosin staining alone. Between 4/1997 and 9/1998 a total of 62 patients with 65 breast cancers underwent surgery. The sentinel node procedure with radio tracers and/or blue dye was performed in patients with clinically negative or unclear positive findings in the axilla, with a primary tumor size less than 5 cm; 11 patients had received preoperative chemotherapy. The sentinel node biopsy was followed by axillary dissection in 44 cases. In 58 (89%) cases we found one or more (on an average 1.4) sentinel nodes with radio tracers (in 73%) and/or the blue dye method (in 85%). Axillary nodal status was correctly predicted in 43 of 44 (97.7%) cases; only in one patient was the sentinel node false negative. After preoperative chemotherapy sentinel nodes were found in 9 cases; all of these were predictive. Micrometastases were found in two patients only after cytokeratine staining. Our results concur with the experience of other study groups in regard of sentinel node biopsy. The sentinel node concept is a fascinating method; its importance in breast cancer treatment appears to be comparable with introduction of breast saving surgery in the 1980's.

Adult↗
PubMed1999

High base pair opening rates in tracts of GC base pairs.

Sequence-dependent structural features of the DNA double helix have a strong influence on the base pair opening dynamics. Here we report a detailed study of the kinetics of base pair breathing in tracts of GC base pairs in DNA duplexes derived from 1H NMR measurements of the imino proton exchange rates upon titration with the exchange catalyst ammonia. In the limit of infinite exchange catalyst concentration, the exchange times of the guanine imino protons of the GC tracts extrapolate to much shorter base pair lifetimes than commonly observed for isolated GC base pairs. The base pair lifetimes in the GC tracts are below 5 ms for almost all of the base pairs. The unusually rapid base pair opening dynamics of GC tracts are in striking contrast to the behavior of AT tracts, where very long base pair lifetimes are observed. The implication of these findings for the structural principles governing spontaneous helix opening as well as the DNA-binding specificity of the cytosine-5-methyltransferases, where flipping of the cytosine base has been observed, are discussed.

Base Pairing↗
PubMed1998

Structure determination and analysis of helix parameters in the DNA decamer d(CATGGCCATG)2 comparison of results from NMR and crystallography.

The solution structure of the DNA decamer (CATGGCCATG)2 has been determined by NMR spectroscopy and restrained molecular dynamic and distance geometry calculations. The restrainted data set includes interproton distances and torsion angles for the deoxyribose sugar ring which were obtained by nuclear Overhauser enhancement intensities and quantitative simulation of cross-peaks from double quantum filtered correlation spectroscopy. The backbone torsion angles were constrained using experimental data from NOE cross-peaks, 1H-1H and 1H-31P-coupling constants. The NMR structure and the crystal structure of the DNA decamer deviates from the structure of the canonical form of B-DNA in a number of observable characteristics. Particularly, both structures display a specific pattern of stacking interaction in the central GGC base triplet. Furthermore, a specific local conformation of the TG/CA base-pair step is present in NMR and crystal structure, highlighting the unusually high flexibility of this DNA duplex part. The solution structure of the TG/CA base-pair step obtained by our high resolution NMR study is characterized by a positive roll angle, whereas in crystal this base-pair step tends to adopt remarkably high twist angles.

Base Pairing↗
PubMed1998

[Malignant hemangioendothelioma of the thyroid gland: new results on pathogenesis, therapy and prognosis].

BACKGROUND: Malignant hemangioendothelioma of the thyroid is a rare tumor predominantly described in areas with endemic goiter like the Alpine regions. The estimated incidence of the disease is between 0.15 and 0.25 per 100,000 inhabitants per year for Western Austria. The prognosis is reported to be dismal. MATERIALS AND METHODS: Between 1982 and 1995, 10 cases with immunohistochemically confirmed malignant hemangioendotheliomas of the thyroid were referred to our department for postoperative or palliative treatment. Two patients with clear margins at surgery received no adjuvant radiotherapy and were only observed. By surgery, clear margins (R-0 resection) were achieved in 5, microscopic residuals (R-1) were left in 3, and gross residual disease in 1 patient. One patient had an inoperable primary tumor. Postoperative radiotherapy was administered in 6 cases, 4 of them additionally received the radiosensitizer razoxane. Total tumor doses ranged between 58 and 65 Gy. RESULTS: Local tumor control was achieved in 9 of 10 patients; 4 of 10 lived longer than 4 years. The median survival time has not yet been reached and is presently between 7.5 and 21+ months.--Noteworthy is a complete regression of 2 lung metastases in a 72-year-old man by a combination of vindesine, razoxane and radiotherapy. The patient is still in complete remission under a maintenance therapy with vindesine and razoxane since 14 months.--It may also be of interest that 4 of the 10 patients were strongly exposed to vinyl chloride and other polymeric materials during their occupational life. CONCLUSIONS: This small series may indicate that the outcome of this disease may not be uniformly deleterious, and that the resistance to radiotherapy reported in the literature may be questioned.--The data offer new evidence of the occurrence of vinyl chloride-induced angiosarcomas outside the liver, and support observations which have already been published in case reports.

Aged↗
PubMed1998

Fourier transform infrared spectroscopy as a probe for the study of the hydration of lipid self-assemblies. I. Methodology and general phenomena.

An algorithm for the study of the gradual hydration of phospholipid assemblies by means of Fourier transform infrared (FTIR) spectroscopy is presented. A complete series of diacyl phosphatidylcholines (PCs) including all possible analogues with palmitoyl and oleoyl residues, namely DPPC, DOPC, POPC, and OPPC, was investigated at room temperature. The lipid samples were prepared as cast films probably consisting of aligned multilamellar bilayers. The range of water activities studied in these films was regulated by adsorption via the gas phase corresponding to relative humidities of between 0 and 100%. Analyses of the IR-spectroscopic data have concentrated mainly on determining the amounts of water incorporated by each lipid as well as the hydration-induced response observed for some absorption bands of the different lipids. The water uptake at high relative humidity (RH) increases with the portion of unsaturated acyl chains in the molecular structure of the PCs. Isothermal phase transitions triggered lyotropically have been detected in demonstrating the occurrence of the main transition in POPC and OPPC films at room temperature. Moreover, it appears that both lamellar phases, the gel as well as the liquid-crystalline phase, are not uniform. They seem to comprise an amazingly large span of order/disorder states of the lipid chains generally depending on the degree of hydration. As exemplified by the significant variation in the onset of wavenumber shifts for the PO2- and C=O stretching-vibration modes, obtained as a function of hydration, a sequence of attachment to polar lipid binding sites by water molecules was established for DPPC.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

The incidence of hyperthyroidism in Austria from 1987 to 1995 before and after an increase in salt iodization in 1990.

Between 1963 and 1990, Austria had iodized salt prophylaxis of endemic goitre with 10 mg KI (7.5 mg I) per kg. This was obviously insufficient, as urinary iodine excretion ranged from 42 to 78 microg I per g of creatinine and goitre in adults remained in the endemic range of 15%-30%. Therefore salt iodization was doubled in 1990. The aim of this study was to assess the annual incidence of different types of hyperthyroidism (HT) before and after this increase in salt iodization. The incidence of HT was recorded in 14 nuclear medicine centres from 1987 to 1995. In five additional centres data were available from 1992 onwards. Data prior to 1992 were documented retrospectively, while those after 1992 were recorded prospectively. The 14 centres drew patients from an area with a population of approximately 4.23 million while all 19 institutes were estimated to cover an area with a population of 5.4 million (the total population of Austria is 7.86 million). A total of 414232 persons were examined for the first time in the participating centres. HT and the type of HT were defined by clinical examination, serum TSH, thyroid hormone levels in blood, ultrasonography, scintigraphy and serum autoantibody titres. HT was classified into immunogenic HT (Graves' or Basedow's disease, GD) and HT with intrinsic thyroid autonomy (uni-, multinodular or disseminated Plummers' disease, PD). HT was also divided into overt (o) or subclinical (sc) disease. The following data were calculated: annual incidence per 100000 and the relative risk (RR) for HT with 95% confidence intervals (CI). In addition, linear trends were calculated for each type of HT by means of logistic regressions. In the 19 centres a total of 47834 patients with HT were registered from 1987 to 1995. PD accounted for 75% of all cases of HT and GD for 19%, while other types of HT were present in 6%. From 1987 to 1989 (time period T0), the annual incidence of oPD was 30.5 (95% CI 29.6-31.5) per 100000. The RR compared to the baseline period T0 was highest in 1992 (1.37; 1.3-1.45) and decreased to 1.17 (1.1-1.24) in 1995. The annual incidence of scPD in T0 was 27.4 (26.5-28.3) per 100000. The RR was highest in 1991 (1.64; 1.56-1.73) and was 1.60 (1. 51-1.69) in 1995. In oPD and scPD a higher RR was observed in persons older than 50 years of age, particularly in men. The incidence of oGD in T0 was 10.4 (9.8-10.9) per 100000; the maximum RR increased to 2.19 (2.01-2.38) in 1993 and decreased to 1.95 (1.78-2.13) in 1995. The incidence of scGD was 1.9 (1.6-2.1) in T0. The maximum RR was observed in 1994 (2.47; 2.04-3.0) and it was still 2.26 (1.85-2.77) in 1995. The increased incidence of oGD and scGD was evenly distributed in all ages and both sexes. The time course of different types of HT following the increase in salt iodization could be divided into two phases: an increase in the incidences of HT with peaks after 1-4 years and a subsequent decrease, the only exception being scGD. The effect was more pronounced in GD than in PD. PD showed an age and gender dependency over time, while GD did not.

Adult↗
PubMed1997

FTIR spectroscopic studies of oligonucleotides that model a triple-helical domain in self-splicing group I introns.

Fourier Transform infrared (FTIR) spectroscopy was used to characterize the Mg2+ dependent association of a 23-mer mixed ribo-deoxyribonucleotide (23-mer RNA) and a 7-mer oligoribonucleotide (7-mer RNA) that models the triple-helical domain of a self-splicing group I intron [Sarkar et al. (1996) Biochemistry 35, 4678-4688]. To elucidate the effect of deoxyribose substitution in the entire backbone, as well as at specific positions, in the assembly of the triple-helical domain, parallel studies were carried out on the association of pure deoxyribonucleotides having base sequences corresponding to the oligoribonucleotides and also between 23-mer RNA and two 7-mer RNA variants. In the variants, either the ribose attached to G451 or the ribose attached to U453 was changed to deoxyribose. FTIR-monitored thermal denaturation of the two 23-mer hairpins shows two distinct melting regions in 1 M NaCl, in case of the RNA hairpin but not for the 23-mer DNA. Triple-helix association between the two strands (7-mer and 23-mer) studied by FTIR show that only when both strands are RNA, association takes place with the formation of the P6 helix. Our results also show that the interactions between the two RNA strands involve some participation of the riboses, which could also involve the 2'-OH groups of the RNA backbone. The assembly of the triple-helical domain is not possible with a deoxyribose backbone and is completely perturbed even when only one ribose at either G451 or U453 position is substituted by deoxyribose.

DNA↗
PubMed1997

Computer analysis of phytochrome sequences and reevaluation of the phytochrome secondary structure by Fourier transform infrared spectroscopy.

A repertoire of various methods of computer sequence analysis was applied to phytochromes in order to gain new insights into their structure and function. A statistical analysis of 23 complete phytochrome sequences revealed regions of non-random amino acid composition, which are supposed to be of particular structural or functional importance. All phytochromes other than phyD and phyE from Arabidopsis have at least one such region at the N-terminus between residues 2 and 35. A sequence similarity search of current databases indicated striking homologies between all phytochromes and a hypothetical 84.2-kDa protein from the cyanobacterium Synechocystis. Furthermore, scanning the phytochrome sequences for the occurrence of patterns defined in the PROSITE database detected the signature of the WD repeats of the beta-transducin family within the functionally important 623-779 region (sequence numbering of phyA from Avena) in a number of phytochromes. A multiple sequence alignment performed with 23 complete phytochrome sequences is made available via the IMB Jena World-Wide Web server (http://www.imb-jena.de/PHYTO.html). It can be used as a working tool for future theoretical and experimental studies. Based on the multiple alignment striking sequence differences between phytochromes A and B were detected directly at the N-terminal end, where all phytochromes B have an additional stretch of 15-42 amino acids. There is also a variety of positions with totally conserved but different amino acids in phytochromes A and B. Most of these changes are found in the sequence segment 150-200. It is, therefore, suggested that this region might be of importance in determining the photosensory specificity of the two phytochromes. The secondary structure prediction based on the multiple alignment resulted in a small but significant beta-sheet content. This finding is confirmed by a reevaluation of the secondary structure using FTIR spectroscopy.

Amino Acid Sequence↗