No abstract available

[en] A method for calculating small-angle scattering profiles using Monte Carlo simulation of the scattering volume is described. From the simulated volume the distance distribution function is calculated directly and a simple Fourier transformation produces the scattering profile. The method is easy to apply to molecules of any shape and composition. Here it is tested against the theoretical profile for a sphere and for an ellipsoid. Finally, the method is applied to a scatterer composed of three spheres connected by a long rod (a model for the biomolecule fibrinogen). (orig.)

[en] The proton resonances of the following synthetic linear human fibrinogen-like peptides were completely assigned with two-dimensional NMR techniques in solution: Ala(1)-Asp-Ser-Gly-Glu-Gly-Asp(7)-Phe-Leu-Ala-Glu-Gly(12)-Gly(13)-Gly(14)-Val(15)-Arg(16)-Gly-Pro-Arg-Val-Val-Glu-Arg (F10), Ala-Asp-Ser-Gly-Glu-Gly-Asp-Phe-Leu-Ala-Glu-Gly-Gly(13)-Gly(14)-Val-Arg (F11), and Gly-Pro-Arg-Val-Val-Glu-Arg (F12). No predominant structure was found in the chain segment from Ala(1) to Gly (6) for F10 in both H₂O and dimethyl sulfoxide. The previous suggestion that there is a hairpin loop involving residues Gly(12) to Val(15) in the Aα chain of human fibrinogen is supported by the slow backbone NH exchange rates of Gly(14) and Val(15), by an unusually small NH chemical shift of Val(15), and by strong sequential NOE's involving this region in F10. This local chain fold within residues Asp(7) to Val(20) may place the distant Phe residue near the Arg(16)-Gly(17) peptide bond which is cleaved by thrombin

[en] The patent deals with a method of locating thrombi in vivo, comprising the steps of administering a radiolabelled peptide selected from the group consisting of Fragment E₁ isolated from cross-linked fibrin, Fragment E₂ isolated from cross-linked fibrin, and peptides having an amino acid sequence intermediate between Fragments E₁, and E₂ derived from cross-linked fibrin by plasmin digestion to a human or animal wherein the peptide, is selectively incorporated or bound by forming a preformed thrombi and externally detecting the radiation emitted by the radiolabelled peptide. A composition containing the peptide used for locating thrombi is also disclosed. 6 tabs

[en] Short communications only

[en] Apolipoprotein(a) [apo(a)] is a glycoprotein with M/sub r/ ∼ 280,000 that is disulfide linked to apolipoprotein B in lipoprotein(a) particles. Elevated plasma levels of lipoprotein(a) are correlated with atherosclerosis. Partial amino acid sequence of apo(a) shows that it has striking homology to plasminogen. Plasminogen is a plasma serine protease zymogen that consists of five homologous and tandemly repeated domains called kringles and a trypsin-like protease domain. The amino-terminal sequence obtained for apo(a) is homologous to the beginning of kringle 4 but not the amino terminus of plasminogen. Apo(a) was subjected to limited proteolysis by trypsin or V8 protease, and fragments generated were isolated and sequenced. Sequences obtained from several of these fragments are highly (77-100%) homologous to plasminogen residues 391-421, which reside within kringle 4. Analysis of these internal apo(a) sequences revealed that apo(a) may contain at least two kringle 4-like domains. A sequence obtained from another tryptic fragment also shows homology to the end of kringle 4 and the beginning of kringle 5. Sequence data obtained from the two tryptic fragments shows homology with the protease domain of plasminogen. One of these sequences is homologous to the sequences surrounding the activation site of plasminogen. Plasminogen is activated by the cleavage of a specific arginine residue by urokinase and tissue plasminogen activator; however, the corresponding site in apo(a) is a serine that would not be cleaved by tissue plasminogen activator or urokinase. Using a plasmin-specific assay, no proteolytic activity could be demonstrated for lipoprotein(a) particles. These results suggest that apo(a) contains kringle-like domains and an inactive protease domain

No abstract available

[en] It became apparent in 1978 that some radioassays for Vitamin B-12 were falsely normal. This investigation was performed to assure the accuracy of our assay. False normal B-12 levels may result in permanent damage or delay in relieving distressful symptoms. False low levels result in no permanent sequalae. ''Normal'' values should be set with these consequences in mind. The authors reviewed clinical charts on patients with <300 pg/m1 serum B-12 in 1000 consecutive determinations and all patients newly diagnosed B-12 deficient 1/1/83 to 10/14/83. Simu1TRAC Radioassay, Becton Dickinson Co., modified by correction for serum nonspecific binding is used. ''Normal'' values (234-1000 pg/m1) are based on 47 outpatients. 176 of the 1000 assays resulted in levels <300 pg/m1. 87 were from other location with no clinical information. 89 assays on Marshfield Clinic patients included 2 duplicates. 45 patients were newly diagnosed B-12 deficient 1/1/83 to 10/14/83. 12 were diagnosed elsewhere and on therapy. 32 had assays <234 pg/m1. 1 with normal B-12 is ''possibly deficient'', a Schilling test is scheduled. The authors conclude that their B-12 assay has correctly identified 32 clinically accepted B-12 deficient patients. 1 possibly deficient patient was normal. 25 of 42 patients with levels below normal are deficient. The false positive rate is felt acceptable in view of the false negative rate and the consequences of the respective errors

[en] The identification of structural markers for B₁₂/protein interactions is crucial to a complete understanding of vitamin B₁₂ transport and metabolic reaction mechanisms of B₁₂ coenzymes. Fourier transform infrared spectroscopy can provide direct measurements of changes in the side chains and corrin ring resulting from B₁₂/protein interactions. Using FTIR spectroscopy in various solvent systems, the authors have identified structural markers for corrinoids in the physiological state. They assign the major band (denoted B), which occurs at ca. 1,630 cm^-1 in D₂O and ca. 1675 cm^-1 in ethanol, to the amide I C double-bond stretching mode of the propionamide side chains of the corrin ring. The lower frequency of band B in D₂O versus ethanol is due to the greater hydrogen-bonding properties of D₂O that stabilize the charged amide resonance form. Since the propionamides are known to be important in protein binding, band B is a suitable marker for monitoring the interaction of these side chains with proteins. They assign bands at ca. 1,575 and 1,545 cm^-1 (denoted C and D) as breathing modes of the corrin ring on the basis of the bands' solvent independence and their sensitivity to changes in axial ligation

[en] A method of fibrinogen preparation is presented in order to label it with ^99mTc employing Sn as reducing agent in alkaline medium. Purity controls by chromatography, coagulation in rabbits and biodistribution in rats were performed. It is concluded that optimal time incubation is between 22 and 23 hs. (M.E.L.)