Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Fragmentation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2005

Fragmentation channels of large multicharged clusters.

We address unifying features of fragmentation channels driven by long-range Coulomb or pseudo-Coulomb forces in clusters, nuclei, droplets, and optical molasses. We studied the energetics, fragmentation patterns, and dynamics of multicharged (A+)n (n=55, 135, 321) clusters. In Morse clusters the variation of the range of the pair-potential induced changes in the cluster surface energy and in the fissibility parameter X=E(Coulomb)2E(surface). X was varied in the range of X=1-8 for short-range interactions and of X=0.1-1.0 for long-range interactions. Metastable cluster configurations were prepared by vertical ionization of the neutral clusters and by subsequent structural equilibration. The energetics of these metastable ionic clusters was described in terms of the liquid drop model, with the coefficients of the volume and surface energies depending linearly on the Morse band dissociation energy. Molecular-dynamics simulations established two distinct fragmentation patterns of multicharged clusters that involve cluster fission into a small number of large, multicharged clusters for X<1 and Coulomb explosion into a large number of individual ions and small ionic fragments for X>1. The Rayleigh instability limit X=1 separates between spatially anisotropic fission and spatially isotropic Coulomb explosion. Distinct features of the fragmentation energetics and dynamics were unveiled. For fission of n=55 clusters, large kinetic and internal energies of the large fragments are exhibited and the characteristic fragmentation time is approximately 700 fs, while for Coulomb explosion the major energy content of the small fragments involves kinetic energy and the characteristic fragmentation time of approximately 300 fs is shorter. The Rayleigh (X=1) limit, leading to isotropic Coulomb explosion, is transcended by a marked enhancement of the Coulomb energy, which is realized for extremely ionized clusters in ultraintense laser fields, or by a dramatic reduction of the surface energy as is the case for the expansion of optical molasses.

Journal Article↗
PubMed1982

Conformational dynamics of a biologically active three-fragment complex of horse cytochrome c.

The conformational dynamics of a biologically active noncovalent complex containing three fragments, ferroheme fragment (1-25)H and apofragments (28-38) and [3H](56-104) [or [3H](39-104)], of horse cytochrome c has been studied with respect to kinetics and thermodynamics of dissociation. The rate of unfolding of the two-fragment complex ferro(1-25)H . (56-104) was also estimated. The results indicate that the ferrous three-fragment complex exhibits a higher frequency of dissociation-association with fragment (28-38) and a lower frequency of overall unfolding-folding at pH 7.0. In the presence of an excess of free (28-38) and below 30 degrees C, unfolding of the ferrous three-fragment complex appears to occur by activation to the transitional state without a large change in conformation, followed by virtually simultaneous dissociation of all three of the fragments [without going through the complex (1-25)H . (56-104), which is a major intermediate for folding]. Above 30 degrees C unfolding via the complex (1-25)H . (56-104) becomes detectable because the equilibrium between the two- and the three-fragment complex is highly temperature dependent. Thus, the relative probabilities of these two different ways of transition for unfolding are modulated by temperature. The observations suggest that the mode of activation of protein and hence the pathway for unfolding may vary depending on temperature. It is also suggested that the interatomic interactions binding the three fragments together in the ordered complex are linked to strengthen each other in the ground state.

Animals↗
PubMed2004

Distribution of breakpoints and fragment sizes in human chromosome 5 after heavy-ion bombardment.

PURPOSE: To measure the location of heavy ion-induced residual breakpoints in human chromosome 5 and the size distribution of chromosome fragments involved in inter- or intrachromosomal exchanges. MATERIALS AND METHODS: Human peripheral blood lymphocytes were exposed to 4 Gy accelerated 56Fe (iron) ions (500 MeV per nucleon (MeV n(-1)), linear energy transfer=200 keV microm(-1)). Cells were then stimulated to grow in vitro for 48 h, and chromosomes were prematurely condensed by calyculin A. Chromosome 5 was painted using high-resolution multicolour banding. The location of the observed residual breakpoints and the size of all chromosome 5 fragments involved in structural aberrations were measured using dedicated image analysis software. RESULTS: Mapping of 283 breakpoints revealed a slight deviation from randomness, with an excess of breakpoints clustered in two small bands and an under representation of breaks at the telomeric end in the q-arm. Breakpoints per unit length were similar in p- and q-arms. The distribution of chromosome fragments has a maximum for very small fragments (< 10% of the chromosome size), indicating a severe fragmentation of chromosome 5 after heavy-ion bombardment. Only fragments < 40% of the chromosome size were involved in intrachromosomal exchanges (interstitial deletions or inversions), whereas fragments up to 75% of the whole chromosome 5 were found in interchromosomal exchanges. CONCLUSIONS: Residual breakpoints after exposure to high-energy iron ions were not distributed randomly along chromosome 5, although the p- and q-arms displayed similar radiosensitivity. Large fragments are either restituted or misrejoined to other chromosome ends, whereas small intrachromosomal fragments can produce either inter- or intrachromosomal exchanges.

Chromosome Breakage↗
PubMed1997

Relationship between PCC fragments and cell killing studied in X-irradiated CHO, CHO-K1 cells and two radiosensitive mutants xrs1 and xrs5.

PURPOSE: To investigate the correlation between PCC fragments and cell killing. MATERIALS AND METHODS: Induction and repair of DNA fragments were measured in CHO, CHO-K1, xrs1 and xrs5 cells using the premature chromosome condensation (PCC) technique and cell survival was determined by a colony assay. RESULTS: The number of PCC fragments measured in cells immediately fused after X-irradiation was the same for CHO (3.4 +/- 0.16/cell/Gy) and CHO-K1 (3.6 +/- 0.12/cell/Gy) cells but significantly higher for xrs1 (4.9 +/- 0.07/cell/Gy) and xrs5 cells (7.0 +/- 0.4/cell/Gy). The repair curve of PCC fragments studied for CHO, CHO-K1 and xrs5 cells was best described by a monophasic exponential decline with a final plateau; the half-time of this decline was always about 30 min. The number of unrejoined PCC fragments, which was measured 14h after irradiation, increased linearly with dose. The steepest increase was found for xrs5 cells (5.5 +/- 0.3 fragments per cell and per Gy), the lowest for CHO/CHO-K1 (0.9 +/- 0.1; 1.0 +/- 0.1) and for xrs1 in between (3.3 +/- 0.1). For all four cell lines the relationship between cell killing and unrejoined fragments could be described by a single curve with a D0 of 2.5 +/- 0.4 unrejoined PCC fragments per lethal event. CONCLUSIONS: The data showed that the number of unrejoined PCC fragments can be used as an indicator of cellular radiosensitivity.

Animals↗
PubMedDate not supplied

CT attenuation value and shockwave fragmentation.

PURPOSE: To evaluate whether, in principle, the mean CT attenuation values of kidney stones could predict fragmentation by shockwaves. MATERIALS AND METHODS: Four types of artificial kidney stones having different CT attenuation values were tested. Artificial stones were weighed and exposed to 700 shockwaves at 21 kV at the focus of an electrohydraulic lithotripter. Fragments were strained through meshes with 2x2-mm and 3.1x3.1-mm openings. The material left on the meshes after shockwave exposure was dried and weighed on a precision scale. Half of all artificial stones were saturated by immersing them in water several days before fragmentation. Fragmentation coefficients (i.e., percent weight loss) were associated with CT attenuation values using a statistical model. RESULTS: Higher CT numbers resulted in lower fragmentation coefficients. Artificial stone weight was inversely proportional to the percent weight loss. Larger fragments were obtained at lower fragmentation coefficients. Statistical analysis revealed that fragmentation can be predicted knowing the weight and the CT number of a stone before shockwave application. CONCLUSION: Prediction of the number of shockwaves necessary for successful SWL could be possible. Our statistical model proved to fit in vitro fragmentation of artificial stones; however, clinical application requires further research.

Humans↗
PubMed1988

Monoclonal antibody to fibrin D-dimer (DD-3B6) recognizes an epitope on the gamma-chain of fragment D.

Laboratory determination of fibrinolysis has been facilitated by diagnostic tests that use monoclonal antibody DD-3B6 to measure fibrin D-dimer levels in plasma. When DD-3B6 is reacted with soluble fibrin fragments, it is specific for fragment D-dimer. The authors have used immunoblot analysis of DD-3B6 binding to purified fragment D and fragment D-dimer to localize the binding site of the antibody. Although DD-3B6 recognizes only fragment D-dimer in solution, it binds to both immobilized fragment D-dimer and fragment D in immunoblots. When immunoblots were performed using protein which was electrophoresed under reducing conditions, DD-3B6 bound to the gamma-chain of fragments D1, D2, and D3. Therefore, the epitope recognized by DD-3B6 resides between amino acids 86 and 302 in the gamma-chain of fragment D. This epitope is masked in soluble non-cross-linked or nondegraded fibrin, but becomes expressed after cross-linked fibrin has been cleaved by plasmin.

Antibodies, Monoclonal↗
PubMed2005

Cytoplasmic fragmentation in activated eggs occurs in the cytokinetic phase of the cell cycle, in lieu of normal cytokinesis, and in response to cytoskeletal disorder.

The timing of cytoplasmic fragmentation in relation to the cell cycle was studied in mature oocytes and early cleavage stages using mouse oocytes and embryos as experimental models. The central approach was to remove the nuclear apparatus, in whole or in part, from non-activated and activated oocytes and early embryos, and follow their response during subsequent culture in vitro. Oocytes arrested in metaphase of the second meiotic division did not fragment following complete removal of the meiotic apparatus, provided they were not subsequently activated. Exposure of spindle-chromosome-complex-depleted oocytes to activation conditions immediately after enucleation led to fragmentation, although not until control embryos entered first mitosis. Delaying activation until 24 h post-enucleation led to earlier fragmentation. Enucleation of normally fertilized or artificially activated oocytes after emission of the second polar body also led to fragmentation coinciding with the first mitosis in nucleated control embryos. However, if artificially activated oocytes were prevented from completing second meiosis, by exposure to cytochalasin, and then enucleated, this universal wave of fragmentation was preceded in some cytoplasts by limited fragmentation after just a few hours in culture, and coinciding with completion of meiosis II in nucleated oocytes. Fragmentation also occurred in the second mitotic cell cycle, but it was limited to blastomeres of fertilized oocytes that were enucleated in late interphase. These results indicate that fragmentation in oocytes and early embryos, though seemingly uncoordinated, is a precisely timed event that occurs only in mitotically active cells, during the cytokinetic phase of the cell cycle, in lieu of normal cytokinesis, and in response to altered cytoskeletal organization.

Animals↗
PubMed1994

A program for selecting DNA fragments to detect mutations by denaturing gel electrophoresis methods.

A computer program was developed to automate the selection of DNA fragments for detecting mutations within a long DNA sequence by denaturing gel electrophoresis methods. The program, MELTSCAN, scans through a user specified DNA sequence calculating the melting behavior of overlapping DNA fragments covering the sequence. Melting characteristics of the fragments are analyzed to determine the best fragment for detecting mutations at each base pair position in the sequence. The calculation also determines the optimal fragment for detecting mutations within a user specified mutational hot spot region. The program is built around the statistical mechanical model of the DNA melting transition. The optimal fragment for a given position is selected using the criteria that its melting curve has at least two steps, the base pair position is in the fragment's lowest melting domain, and the melting domain has the smallest number of base pairs among fragments that meet the first two criteria. The program predicted fragments for detecting mutations in the cDNA and genomic DNA of the human p53 gene.

Algorithms↗
PubMed1977

Mapping and cloning of Eco RI-fragments of bacteriophage T5+ DNA.

The Eco RI-fragments of bacteriophage T5 DNA were mapped using a technique which involves primarily length measurements of molecules observed in the electron microscope. Since Eco RI cleavage generates termini with 4-nucleotide long cohesive ends, fragments of complete and partial Eco RI digests were covalently circularized with DNA ligase at dilute DNA concentrations before measuring relative to internal length standards. This established the order of the internal Eco RI fragments. The two external Eco RI fragments, which had only one Eco RI terminus, were positioned relative to the internal fragments by identifying the location of some of the naturally-occurring nicks in partially denatured linear Eco RI fragments. An attempt was made to clone each of the internal Eco RI-fragments of T5 DNA via transformation into E. coli after ligation in vitro with the plasmid pMB 9. Only one fragment could be cloned and this fragment did not specify any new polypeptides in minicells of either the E. coli EK1 host, X1411, or the EK 2 host, X1776.

Chromosome Mapping↗
PubMed1979

Interaction of myosin subfragment-1 with actin. II. Location of the actin binding site in a fragment of subfragment-1 heavy chain.

The heavy chain of subfragment-1 prepared by chymotrypsin treatment had a molecular weight of about 96K. The heavy chain was split into 26 K, 50 K, and 21 K fragments by trypsin. When the trypsin-treated subfragment-1 was cross-linked with dimethyl suberimidate, cross-linked products of 26 K, 50 K, and 21 K fragments and of 50 K and 21 K fragments appeared, but there was little cross-linked product of 26 K and 50 K fragments or of 26 K and 21 K fragments. When the cross-linking experiments were carried out in the presence of actin, a new band appeared and the amount of cross-linked product of 26 K, 50 K, and 21 K fragments decreased by about 50%. The molecular weight of the new band was lower than that of the cross-linked product of 26 K, 50 K, and 21 K fragments, and higher than that of the dimer of actin. Based on this and some other results, we suggest that this band represented a cross-linked product of actin and the 50 K fragment. We also suggest that the decrease in the amount of cross-linked product of 26 K, 50 K, and 21 K fragments reflected the conformational change in subfragment-1 due to the binding of actin.

Actins↗
PubMed2002

The effect of sleep fragmentation on daytime function.

It is clear from this literature that fragmented sleep is less restorative than consolidated sleep, and leads to sleepiness-related daytime impairment. The optimal approach to the quantification of sleep fragmentation continues to be debated. Modest and erratic correlations between measures of sleepiness and traditional measures of EEG arousals have pushed investigators to try and find more sensitive measures of sleep fragmentation. Simply correlating various measures of sleep fragmentation with a measure of sleepiness has significant limitations. Since sleep fragmentation is not the only factor affecting daytime sleepiness, these correlations can be misleading. For example, a subject with severely fragmented sleep will show elevated sleepiness during the day. However, the overall correlation may be reduced because lack of fragmented sleep does not guarantee that the level of sleepiness will be low. Multivariate statistical modeling is needed to account for sources of variance simultaneously in the prediction of daytime sleepiness. In this way it may be possible to identify the optimal definition of sleep fragmentation. More studies are needed that evaluate "sub-cortical" arousals, EEG arousals, and daytime function simultaneously. Ideally, clarification of these measurement issues will lead to an improved understanding of sleep structure and the mechanism through which sleep fragmentation impacts daytime function.

Adult↗
PubMed2003

Waking quantitative electroencephalogram and auditory event-related potentials following experimentally induced sleep fragmentation.

STUDY OBJECTIVES: Experimental sleep fragmentation involves inducing arousals by administering intrusive auditory stimuli throughout the night. It is intended to model the frequent and periodic disruption experienced in common sleep disorders. Sleep fragmentation leads to daytime sleepiness, although evidence of performance impairment has been inconsistent. The purpose of this study was to investigate brain physiology associated with this level of sleep disruption. Specifically, quantitative analysis of electroencephalography was carried out, and auditory event-related potentials were recorded during daytime performance assessment following sleep fragmentation in good sleepers. DESIGN: Participants spent 4 consecutive 24-hour periods in the laboratory. On nights 2 and 3, sleep was fragmented using auditory stimuli that were delivered with increasing intensity until an arousal was noted. This design aimed to investigate the cumulative effects of sleep fragmentation on daytime functioning. SETTING: Data were collected in a sleep research laboratory during a 96-hour protocol. PARTICIPANTS: Eight healthy adults (mean age = 33.25) with no sleep complaints. MEASUREMENTS AND RESULTS: During the day, participants performed a 40-minute computerized test battery at 2-hour intervals (9:00 am -7:00 pm). The battery was presented in a fixed order and included measures of mood, sleepiness, reaction time, and serial addition or subtraction. Results indicated that subjective sleepiness and mood were impaired following sleep-fragmentation nights, compared to both baseline and recovery conditions. No performance deficits were apparent. The alpha:theta ratio, reflecting relative slowing of the electroencephalogram, was dramatically reduced following the second night of sleep fragmentation. Reductions in N1 amplitude of the event-related potentials indicated that attention was impaired with respect to early encoding processes following sleep fragmentation. CONCLUSIONS: Electroencephalographic and event-related potentials data illustrate impairment in information-processing capabilities associated with reduced arousal elicited by experimental sleep fragmentation. This subtle degree of sleep disruption, where total sleep time is not reduced, leads to sustained impairment in alertness and attention.

Adult↗
PubMed1988

Imaging thrombi with radiolabelled fragment E1.

Fragment E1 is a fragment of human fibrin, produced by controlled plasmin digestion of cross-linked fibrin. It comprises the N-terminal regions of all six polypeptide chains of fibrin. It has been shown to contain a pair of dimeric binding sites which are complementary in binding to sites in the D domains of fibrin which are formed when fibrin polymerizes, so fragment E1 binds to fibrin dimers and polymers but not fibrin monomer or fibrinogen. Radioiodinated fragment E1 has been shown to localize in venous thrombi in a pig model. Thrombus/blood ratios of up to 100: 1 were obtained at 24 h post injection, in thrombi up to 5 days old at the time of tracer injection. In humans, deep-venous thrombi were visualized within 30 min of 123I-labelled fragment E1. Fragment E1 exhibits very rapid blood disappearance, which enhances its ability to produce high thrombus/blood ratios at early times. The thrombus uptake of labelled fragment E1 is not affected by heparin. Fragment E1 has been derivatized with metal chelating groups [diethylene-triaminepentaacetic acid (DTPA) and deferoxamine], to facilitate labelling with 111In and 67Ga. Although these labels appeared promising in animal models, they have not yet achieved success in man. Clinical trials are continuing with 123I-labelled fragment E1, which is felt to be a most promising radiopharmaceutical for thrombus localization.

Animals↗
PubMed2003

Evaluation of synchronous twin pulse technique for shock wave lithotripsy: determination of optimal parameters for in vitro stone fragmentation.

PURPOSE: The Twinheads extracorporeal shock wave lithotriptor (THSWL) is composed of 2 identical shock wave generators and reflectors. One reflector is under the table and the other is over the table with a variable angle between the axes of the 2 reflectors. The 2 reflectors share a common second focal point, making it possible to deliver an almost synchronous twin pulse to the targeted stone. We studied the optimal parameters for in vitro stone fragmentation. MATERIALS AND METHODS: Two types of 1 cm artificial stones were used, namely Bon(n)-stones of 3 compositions (75% calcium oxalate monohydrate [COM] plus 25% uric acid, struvite and cystine) and plaster of Paris. The parameters tested were shock wave number (100, 500 and 1,000), shock wave power (8, 11 and 14 kV) and angle between the reflector axes (67, 90 and 105 degrees). After the optimal parameters were determined we studied the disintegrative efficacy of THSWL for 3 types of human urinary calculi, including COM, calcium hydrogen phosphate (brushite) and cystine. Each stone received 1,000 twin shock waves at 14 kV with an angle of 90 degrees between the reflectors. All experiments were done using a rate of 60 twin shock waves per minute. Following lithotripsy stone fragments were processed and sized. The ratio of the weight of fragments greater than 2 mm-to-total weight of all fragments was calculated. RESULTS: Optimal stone fragmentation results for THSWL were obtained with the maximum number of shock waves (1,000) and full power (14 kV). There was no significant statistical difference in fragment size or the ratio of fragments greater than 2 mm with the use of different angles except for cystine and plaster of Paris calculi, for which the right angle was most effective. At application of the optimal parameters to human stones THSWL produced small fragment size for COM and cystine stones, while brushite stones were not fragmented to the same extent. CONCLUSIONS: The efficacy of synchronous twin pulse technology improves as the number of shock waves and power increase. A 90-degree angle between the shock wave reflectors is advantageous for certain stones (that is cystine and plaster of Paris) but it is not a factor for other stone compositions. THSWL has satisfactory disintegrative efficacy for human stones, especially COM and cysteine calculi.

Calcium Oxalate↗
PubMed2004

In vitro comparison of fragmentation efficiency of flexible pneumatic lithotripsy using 2 flexible ureteroscopes.

PURPOSE: Pneumatic lithotripsy has been shown to be an effective and safe intracorporeal lithotripsy modality for renal and ureteral calculi, capable of fragmenting stones of all compositions. We determined the in vitro stone fragmentation abilities of the 0.5 mm flexible pneumatic lithotripsy probe when inserted through the working channel of 2, 7.5Fr flexible ureteroscope designs (straight working channel and offset working channel at approximately 30 degrees from the long axis of the endoscope). The velocity and displacement of the pneumatic probe tip were also evaluated with the probe inserted through each endoscope. MATERIALS AND METHODS: The 0.5 mm (1.5Fr) stainless steel probe was tested at 5 deflection angles, namely 0, 12, 24, 33 and 48 degrees, at a pneumatic pressure of 2.5 bar when inserted through the offset and straight working channel ureteroscopes. A noncontact optical laser system was used to measure or calculate the displacement and velocity of the 0.5 mm probe tip at each angle of deflection with the 2 ureteroscopes. Fragmentation at all deflection angles was assessed using plaster of Paris stone phantoms with the pneumatic device on continuous mode at 2.5 bar pressure for 30 seconds. Stones were weighed after each fragmentation cycle and the percent weight lost was determined. Comparisons were made between the 2 ureteroscopes at each angle. RESULTS: Probe tip displacement was significantly better through the straight channel ureteroscope with 30% improvement at all angles tested compared to the offset channel. Moreover, a substantial decrement in tip displacement was noted as the angle of deflection increased regardless of the endoscope used. Conversely tip velocity was relatively unchanged throughout the study and it was equivalent from straight to offset channel measurements. Phantom stone fragmentation correlated inversely with the severity of the deflection angle. An approximately 80% loss of fragmentation ability was noted as the angle increased from 0 to 48 degrees. Although the pneumatic device performed better through the straight channel scope, a similar percent loss in fragmentation from 0 to 48 degrees was seen when using either endoscope. CONCLUSIONS: The flexible pneumatic 0.5 mm lithotripsy probe appears to be best used through a straight channel flexible ureteroscope, out performing use through the offset channel scope at all angles of deflection. Tip displacement and fragmentation ability were inversely related to the degree of active deflection as the angle increased from 0 to 48 degrees. Use of the flexible pneumatic probe to aid in managing renal or proximal ureteral calculi may be limited until an improved probe can be developed, allowing complete and unencumbered fragmentation throughout all angles of deflection.

Biomechanical Phenomena↗
PubMed2003

Scaling of impact fragmentation near the critical point.

We investigated two-dimensional brittle fragmentation with a flat impact experimentally, focusing on the low-impact-energy region near the fragmentation-critical point. We found that the universality class of fragmentation transition disagreed with that of percolation. However, the weighted mean mass of the fragments could be scaled using the pseudo-control-parameter multiplicity. The data for highly fragmented samples included a cumulative fragment mass distribution that clearly obeyed a power law. The exponent of this power law was 0.5 and it was independent of sample size. The fragment mass distributions in this regime seemed to collapse into a unified scaling function using weighted mean fragment mass scaling. We also examined the behavior of higher-order moments of the fragment mass distributions, and obtained multiscaling exponents that agreed with those of the simple biased cascade model.

Journal Article↗
PubMed2006

Automated reassembly of file fragmented images using greedy algorithms.

The problem of restoring deleted files from a scattered set of fragments arises often in digital forensics. File fragmentation is a regular occurrence in hard disks, memory cards, and other storage media. As a result, a forensic analyst examining a disk may encounter many fragments of deleted digital files, but is unable to determine the proper sequence of fragments to rebuild the files. In this paper, we investigate the specific case where digital images are heavily fragmented and there is no file table information by which a forensic analyst can ascertain the correct fragment order to reconstruct each image. The image reassembly problem is formulated as a k-vertex disjoint graph problem and reassembly is then done by finding an optimal ordering of fragments. We provide techniques for comparing fragments and describe several algorithms for image reconstruction based on greedy heuristics. Finally, we provide experimental results showing that images can be reconstructed with high accuracy even when there are thousands of fragments and multiple images involved.

Algorithms↗
PubMed1976

Transcription in vitro of phi29 DNA and EcoRI fragments by Bacillus subtilis RNA polymerase.

EcoRI fragments A, B and C produced from linear phi29 DNA, but not D or E fragments, are transcribed by purified Bacillus subtilis RNA polymerase. The transcription of fragments A and C is initiated preferentially with GTP and to a lesser extent with ATP; the reverse happens in the case of fragment B. The dinucleotides GpU and GpA respectively, compete specifically with the incorporation of [gamma-32P]GTP directed by fragments A and C. The RNA synthesized in vitro by purified B. subtilis RNA polymerase is highly asymmetric. Most of the RNA synthesis directed by fragments A and C is early RNA. However, most of the RNA produced by fragment B is anti-late-RNA. Addition of crude extracts inhibit the transcription of fragment B but not that of fragments A and C.

Bacillus subtilis↗