共查询到20条相似文献,搜索用时 31 毫秒
1.
New approach to the mass spectroscopy of non-volatile compounds 总被引:3,自引:0,他引:3
D F Torgerson R P Skowronski R D Macfarlane 《Biochemical and biophysical research communications》1974,60(2):616-621
A new method has been developed to obtain mass spectra of non-volatile compounds from the solid state at room temperature. Volatilization and chemical ionization of the sample are effected using a 252Cf fission fragment source. Mass spectra are measured using a new time-of-flight mass spectrometer featuring single ion counting and fast electronics. We present positive and negative ion mass spectra for the amino acids arginine and cystine which are characterized by intense quasi-molecular ions. 相似文献
2.
R D Lloyd C W Mays C W Jones D R Atherton F W Bruenger L R Shabestari M E Wrenn 《Radiation research》1984,100(3):564-575
Equations have been derived, from the results of total-body and partial-body counting and gamma-ray counting of individual bones and soft tissues, which describe the retention of injected 241Am in the liver, in the nonliver tissue (including skeleton), and in the skeleton of young adult beagles. Retention was found to be dependent upon injection level, and different sets of equations were developed for dogs given about (a) 2.8 microCi/kg (b) 0.9 microCi/kg (c) 0.3 microCi/kg, and (d) 0.1 microCi/kg and less. Liver rention, RL, was characterized by a single exponential equation of the form RL = ce-beta t, with c = 0.49 +/- 0.04 and beta = a function of injection level. Nonliver tissue was assigned a retention equation of the form RNL = d + alpha + J(l - e-mt), with d = 0.102 +/- 0.024 e-1.22t, alpha = 0.41 +/- 0.04, and both J and m as a function of injection level. Skeletal retention was found to be about 0.885 +/- 0.037 of nonliver retention with no significant dependence upon either injection level or time after 241Am injection. Dosimetry equations based on these retention expressions were derived. Individual bones of 55 beagles were assayed at death for their 241Am content for a determination of 241Am distribution within the skeleton. 相似文献
3.
《Reports of Practical Oncology and Radiotherapy》2019,24(6):660-666
AimThe purpose of this study is to analyse how small variations in the elemental composition of soft tissue lead to differences in dose distributions from a 252Cf brachytherapy source and to determine the error percentage in using water as a tissue-equivalent material.BackgroundWater is normally used as a tissue-equivalent phantom material in radiotherapy dosimetry.Materials and methodsNeutron energy spectra, neutron and gamma-ray dose rate distributions were calculated for a 252Cf AT source located at the center of a spherical phantom filled with various types of tissue compositions: adipose, brain, muscle, International Commission on Radiation Units and Measurements (ICRU) report No. 44 9-component soft tissue and water, using Monte Carlo simulation.ResultsThe obtained results showed differences between total dose rates in various tissues relative to water varying between zero and 4.94%. The contributions of neutron and total gamma ray doses to these differences are, on average, 81% and 19%, respectively. It was found that the dose differences between various soft tissues and water depend not only on the soft tissue composition, but also on the beam type emitted from the 252Cf source and the distance from the source.ConclusionAssuming water as a tissue-equivalent material, although leads to overestimation of dose rate (except in the case of adipose tissue), is acceptable and suitable for use in 252Cf brachytherapy treatment planning systems based on the recommendation by the ICRU that the uncertainties in dose delivery in radiotherapy should be lower than 5%. 相似文献
4.
Bagher Farhood Hadi Samadian Mahdi Ghorbani Seyed Salman Zakariaee Courtney Knaup 《Reports of Practical Oncology and Radiotherapy》2018,23(5):462-473
Neutron capture therapy (NCT) is a targeted radiotherapy for cancer treatment. In this method, neutrons with a spectra/specific energy (depending on the type of agent used for NCT) are captured with an agent that has a high cross-section with these neutrons. There are some agents that have been proposed in NCT including 10B, 157Gd and 33S. Among these agents, only 10B is used in clinical trials. Application of 157Gd is limited to in-vivo and in-vitro research. In addition, 33S has been applied in the field of Monte Carlo simulation. In BNCT, the only two delivery agents which are presently applied in clinical trials are BPA and BSH, but other delivery systems are being developed for more effective treatment in NCT. Neutron sources used in NCT are fission reactors, accelerators, and 252Cf. Among these, fission reactors have the most application in NCT. So far, BNCT has been applied to treat various cancers including glioblastoma multiforme, malignant glioma, malignant meningioma, liver, head and neck, lung, colon, melanoma, thyroid, hepatic, gastrointestinal cancer, and extra-mammary Paget's disease. This paper aims to review physical, dosimetric and clinical aspects as well as delivery systems in NCT for various agents. 相似文献
5.
A F Welton T C Pederson J A Buege S D Aust 《Biochemical and biophysical research communications》1973,54(1):161-167
The molecular weight of detergent-solubilized NADPH-cytochrome c reductase from rat liver microsomes has been estimated to be 79,000. The method used for this determination involves immunoprecipitation of deoxycholate-solubilized enzyme from 125I-labeled microsomal proteins. The antibody was prepared against a purified preparation of Bromelain-solubilized enzyme (molecular weight 71,000). The immunoprecipitate was then subjected to SDS-polyacrylamide gel electrophoresis and the enzyme located by 125I-gamma counting. 相似文献
6.
M. Kadirova Yu. F. Simakhin N. Jumaev M. M. Usmanova 《Biological trace element research》1999,(1):651
To investigate some impurity profiles by (n,α) reactions for destructive and nondestructive analysis, two experimental facilities on a horizontal channel of the well-moderated research reactor have been developed. In accordance with an α-particle registration geometry two different measurement techniques based on using a surfacebarrier Si(Au) detector and a counting ionization chamber have been used. The determination limit of boron is ofn x 1016 cm-3 or (1 /dv 5) x 10-5 % with a depth resolution of ±0.03 Μm in semiconductors. A solid-state nuclear track detector (SSNTD) has also been used to determine the boron surface and deep distributions in semiconductors, plants, and other materials. 相似文献
7.
C W Mays R D Lloyd G N Taylor L R Shabestari W Angus D R Atherton N A Gillett 《Radiation research》1989,119(3):432-442
Thirty beagles and 277 mice were injected with 249Cf, and 30 beagles and 274 mice were injected with 252Cf. The skeletal dose (in Gy) from 252Cf was about half from fission fragments and half from alpha particles, whereas 249Cf emits alpha particles in 100% of its transformations. Bone sarcomas (mostly osteosarcomas) were the main radiation-induced cancer. The relative biological effectiveness (RBE) of fission fragment dose relative to alpha-particle dose for bone sarcoma induction was calculated from the ratio of 249Cf/252Cf doses at equal times to bone sarcoma in (a) beagles and (b) mice, and (c) from the ratio 252Cf/249Cf risk coefficients in mice. The average RBE +/- standard deviation of the three evaluations was 0.1 +/- 0.1. The very low RBE for bone sarcomas is supported by the data of A. L. Batchelor, T. J. Jenner, and L. M. Cobb [Phys. Med. Biol. 28, 475-483 (1983)] for lung cancer induction in rats and by that of A. L. Brooks, J. A. Mewhinney, and R. O. McClellan [Health Phys. 22, 701-706 (1972)] for producing chromosome aberrations in the liver cells of Chinese hamsters. The low effectiveness of fission fragments relative to alpha particles, per gray of absorbed dose, is ascribed primarily to the much larger number of cells traversed by the alpha particles. Consideration might be given to decreasing the quality factor of fission fragments by an order of magnitude below that for alpha particles. 相似文献
8.
M. Kadirova Yu. F. Simakhin N. Jumaev M. M. Usmanova 《Biological trace element research》1999,(1):651
To investigate some impurity profiles by (n,α) reactions for destructive and nondestructive analysis, two experimental facilities on a horizontal channel of the well-moderated
research reactor have been developed. In accordance with an α-particle registration geometry two different measurement techniques
based on using a surfacebarrier Si(Au) detector and a counting ionization chamber have been used. The determination limit
of boron is ofn x 1016 cm-3 or (1 /dv 5) x 10-5 % with a depth resolution of ±0.03 Μm in semiconductors. A solid-state nuclear track detector (SSNTD) has also been used
to determine the boron surface and deep distributions in semiconductors, plants, and other materials. 相似文献
9.
A method using HPLC with electrochemical detection has been developed for the determination of GSH in tissue. The method is based upon the separation of GSH from other components by cation exchange chromatography coupled with the electrochemical oxidation of GSH to the corresponding disulfide. Detection limits of ca. 5 × 10?12 moles GSH were established and the method was used to measure GSH content of rat and guinea pig brain, liver and synaptosome preparations. 相似文献
10.
A procedure which combines thin-layer chromatography with position-sensing proportional counting has been developed for analyzing the metabolism of carcinogenic polycyclic aromatic hydrocarbons. The profiles of the metabolites of [3H]benzo(a)pyrene and 7,12-[12-14C]dimethylbenz(a)anthracene produced in cell culture were comparable when obtained by this procedure and by standard methods. However, position-sensing proportional counting allows simultaneous counting of all components of a sample within 10–20 min, and thereby permits the analysis of many hydrocarbon samples in a short time. In addition, the procedure eliminates the necessity of cutting or scraping carcinogen-containing thin-layer chromatograms. 相似文献
11.
V. I. Vladimirov L. V. Deputatova V. I. Molotkov A. P. Nefedov V. A. Rykov V. S. Filinov V. E. Fortov A. V. Khudyakov 《Plasma Physics Reports》2001,27(1):36-43
Ordered dusty structures formed of spherical monodisperse and polydisperse grains are obtained for the first time in a nuclear-track plasma produced by α-particles and fission fragments of 252Cf nuclei passing through neon or argon. A theoretical model of such a plasma is proposed. Monte Carlo computer simulations based on this model are carried out to explain the formation of such structures. 相似文献
12.
High-efficiency liquid-scintillation counting of 14C-labelled material in aqueous solution and determination of specific activity of labelled proteins 总被引:17,自引:17,他引:0
1. Inexpensive scintillation mixtures are described which enable the detection of as little as 40μμc of 14C in aqueous solution with an efficiency of counting of over 80%. 2. A rapid method for the counting of alkaline, acidic and neutral aqueous solutions of up to 1ml. volume is described. Ethanol or 2-ethoxyethanol is used as blending agent. 3. The scintillation counting of alkaline solutions is applied to the accurate determination of the specific activity of 14C-labelled proteins from plant tissues. 4. Attention has been paid to the importance of a standardized washing procedure for the removal of all traces of radioactive material from glassware. 相似文献
13.
Bengt Jergil Marianne Sommarin 《Biochimica et Biophysica Acta (BBA)/General Subjects》1983,758(1):10-16
A method has been developed to measure the Ca2+- and phospholipid-dependent protein kinase in membrane fractions. The method is based on the fact that this enzyme is resistant to comparatively high concentrations of octyglycoside. Rat liver membranes were treated with octylglycoside and the phosphate incorporation from |-32P]ATP was measured in the presence of histone H1. The enzyme activity was determined as the difference between the incorporation obtained after addition of Ca2+ and phosphatidylserine and the incorporation obtained without these additions but with EGTA. The endogenous incorporation of phosphate to membrane components was constant under these incubation conditions. The conditions for determination of the membrane-bound enzyme were optimized. Two thirds of the total enzymic activity was attached to membranes in rat liver cells. A highly purified plasma membrane preparation had the highest specific activity, while most of the bound enzyme was found in microsomes, an only traces were found in mitochondria. 相似文献
14.
J E Tomaszewski D M Jerina W Levin A H Conney 《Archives of biochemistry and biophysics》1976,176(2):788-798
A radiometric assay for the in vitro metabolism of zoxazolamine has been developed which combines high sensitivity and rapid determination of product. [4,6-3H]zoxazolamine was metabolized to 6-hydroxyzoxazolamine, and the tritium released as 3H2O was determined after treating the incubation mixture with activated charcoal. This treatment efficiently removes labeled substrate (99.98%), permitting enzymatically released tritium to be measured directly in the aqueous medium. Since the preponderant in vitro product of zoxazolamine metabolism by rat liver microsomes and the purified reconstituted mixed function oxidase system is 6-hydroxyzoxazolamine, and since this aryl hydroxylation occurs without significant NIH shift, the subsequent release of tritium from the 6-position accurately represents metabolism of the molecule. The use of [4,6-3H]zoxazolamine for a tritium release assay of mixed function oxidase activity is ideal since this compound shows no significant isotope effect or NIH shift during metabolic conversion to 6-hydroxyzoxazolamine. 3-Methylcholanthrene treatment of rats resulted in a fourfold induction of zoxazolamine hydroxylation while phenobarbital or pregnenolone 16α-carbonitrile pretreatment caused only a 20–50% increase in zoxazolamine metabolism. The use of a purified reconstituted system revealed that cytochrome P-448 from 3-methylcholanthrene-treated rats was approximately 10- to 15-fold more efficient than cytochrome P-450 from phenobarbital-treated rats in catalyzing the hydroxylation of zoxazolamine. 相似文献
15.
J Van Dam G Billiet A Dutreix A Wambersie 《Comptes rendus des séances de la Société de biologie et de ses filiales》1982,176(3):435-441
Relative biological effectiveness (RBE) of 252Cf, with respect to 192Ir, has been determined at the low dose rates commonly used in interstitial and intracavitary therapy. The biological criterion was growth reduction in Vicia faba bean roots. Two varieties of Vicia faba were used. For Vicia faba Sutton's seeds, an RBE of 5.7 to 6.6 was obtained for 252Cf Dn + gamma doses of 0.5 to 0.2 Gy respectively and at a Dn + gamma dose rate of 0.11 Gy-1. The gamma contribution D gamma/Dn + gamma at the level of the root tipes was 0.35 and the derived RBE of the neutron emission of 252Cf was then 8.2 to 9.7. For Vicia faba Be1B and in the same irradiation conditions, an RBE of 5.1 to 6.2 was obtained for the total (n + gamma) 252Cf emission and for Dn + gamma doses of 0.4 to 0.2 Gy respectively. These values lead to an RBE of 7.4 to 9.0 for the neutron emission of 252Cf. For Vicia faba BelB, but for another source arrangement (Dn + gamma dose rate of 0.13 Gy . h-1 for 252Cf), an RBE of 5.6 to 7.5 was obtained for the total (n + gamma) emission of 252Cf and for Dn + gamma doses of 0.4 to 0.1 Gy respectively. The gamma contribution (D gamma/Dn + gamma) at the level of the root tips was 0.42, and the derived RBE of the neutron emission of 252Cf was then 8.9-12.3. 相似文献
16.
H. Fritzsche I. Petri H. Schütz K. Weller P. Sedmera H. Lang 《Biophysical chemistry》1980,11(1):109-119
1) The self-association of both caffeine (Cf) and 5'-adenosine monophosphate (AMP) in aqueous solution has been reinvestigated by 1H NMR. The self-association process is characterized by an isodesmic model. The apparent self-association constants of the vertical stacking process are KCf= (10.6 ± 1.0) M?1 and kamp = (1.67 ± 0.17) M?1. The arrangement of the monomeric units in the stacked aggregates is discussed in terms of isoshielding curves theoretically calculated by Giessner-Prettre and Pullman. Models are proposed which are consistent with these and further previous NMR data. 2) The interaction of Cf and AMP has been studied by ?1 H NMR. The apparent association constant of the complex Cf-AMP is KC-A = (7.3 ± 1.2) M?1.Two models of the mutual arrangement of AMP and Cf in the complex are proposed on the basis of the calculated isoshielding curves considering both ring current and local atomic diamagnetic anisotropy effects. 3) The interaction of Cf and poly(riboadenylate), (rA)n is indicated by a downfield shift of the H-8 line but an upfield shift of the H-2 line in the 1H NMR spectra of (rA)n. The concentration dependence of the 1H NMR shifts of both Cf and (rA)n can be explained by the existence of two binding mechanisms. We suggest (i) partial insertion of Cf between adjacent base residues of ordered single-stranded regions of (rA)n and (ii) outside binding of Cf in form of monomeric Cf as well as of self-associated aggregates. The complex geometry of insertion proposed on the basis of the calculated isoshielding curves is characterized by a stronger overlapping of the Cf ring and the H-2 proton of (rA)n as compared to the H-8 proton. 相似文献
17.
A method has been developed for the determination of low amounts of propionyl-CoA in biological material. The method involves 14CO2 fixation by propionyl-CoA in the presence of purified propionyl-CoA carboxylase. Values for propionyl-CoA in rat liver in vivo and in isolated rat livers perfused in the presence of propionate are reported. 相似文献
18.
A nuclear analytical method, involving activation with3He ions, was developed to determine carbon content in human teeth with well-documented histories. The tooth samples were irradiated with 2.7-MeV3He particles at 50 nA intensity, and the activity of14O induced through the reaction12C(3He, n)14O, determined by counting the 2.31-MeV gammas. Different dental hard tissues were studied separately. A solid piece of silver steel, the carbon content of which was accurately determined by chemical means, was used as the standard. The carbon content in different teeth varied from 4–7%. The overall experimental accuracy was better than 4.5%.
相似文献19.
I. Quantitative determination of the amount of DNA per nucleus by interference microscopy 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A method for the determination of the DNA content of isolated nuclei of different ploidy has been developed. It is based on measurement of the nuclear dry mass, with an integrating microinterferometer, before and after DNase treatment. The values found are slightly low, because, as indicated by biochemical determinations, consistently 5% to 8% of DNA is not extracted by DNase under these conditions. The average DNA values thus obtained for diploid and tetraploid nuclei of adult rat liver are 7.7 and 15.6 pg (10-12 g), respectively. Definite advantages of this procedure are: i) comparisons with biochemical determinations to give DNA values for each class of ploidy, ii) comparisons with histophotometry of the Feulgen dye-DNA complex to give absolute values instead of arbitrary units. 相似文献
20.
Determination of N-(9-( -D-ribofuranosyl)purin-6-ylcarbamoly)threonine at the picomole level in transfer-RNA 总被引:2,自引:0,他引:2
An assay has been developed for quantitation of the modified nucleoside, t6A, in tRNA at the pmole level. For tRNA from a variety of species, the content of t6A was found to be 0.18–0.25 mole %. These values lend support to the suggestion that t6A is located at the 3′-end of the anticodon in tRNA's whose codons begin with adenosine. Essentially no t6A was found in Mycoplasma sp. (Kid) tRNA which is deficient in many modified nucleosides. In the rat, no organ specific differences were found. The amount of t6A in Novikoff hepatoma tRNA was essentially the same as in tRNA from normal rat liver. 相似文献