Fluorescence polarization decay of tyrosine in lima bean trypsin inhibitor

The fluorescence of lima bean trypsin inhibitor is due to a single tyrosine residue at position 69. The lifetime of this tyrosine fluorescence is 620 +/- 50 ps (mean +/- SD) and is little affected by addition of 0.88 M citrate, an efficient quencher of tyrosine fluorescence. The steady-state emission intensity is also only weakly reduced by the quencher. The tyrosine is thus not accessible to the citrate and is probably located in the interior of the protein. The high pK of the tyrosine supports this conclusion. The fluorescence anisotropy decay of the inhibitor's tyrosine can be fitted to a double exponential form, with time constants of about 40 ps and greater than or equal to 3 ns. The anisotropy at time zero is 0.19 +/- 0.015 (mean +/- SD), the same as for N-acetyl-L-tyrosinamide in viscous glycerol solution. The nanosecond component of the decay is consistent with rotation of the entire protein molecule. The 40-ps component demonstrates that the tyrosine has considerable freedom to move independently of the protein as a whole. This rotational correlation time is approximately what is observed for free tyrosine in aqueous solution. Since the polypeptide chain near tyrosine-69 is anchored by several disulfide bonds, the data argue that this interior portion of the protein consists of a rigid, immobile backbone embedded in fluid, mobile amino acid side chains.

[Preparation and preliminary identification of the monoclonal antibody against esophageal carcinoma]

A series of monoclonal antibody against esophageal carcinoma was prepared by ECa109 cells immunizing Balb/c mice. Hybrids secreting antibodies reacting to ECa109 were isolated and further cloned. One monoclonal antibody, 4C3, reacted only to an esophageal cancer cell line, gastric cancer and hepatocellular carcinoma cell lines. Purified 4C3 was used in ELISA test to detect tumor cells in the esophageal epithelial cells obtained by friction balloon. The result showed that the concordance rate to the result of balloon cytosmear was 62.4% (73/117). Patients, diagnosed cytologically as dyskaryosis, were often positive in ELISA test. It is proposed that 4C3 be useful in detecting pre-cancerous lesions.

The role of metaphosphate in the activation of the nucleotide by TPS and DCC in the oligonucleotide synthesis

The course of the activation of 3'-acetylthymidine 5'-phosphate by TPS and DCC were followed up by 31P FT nmr. The fact that the "metaphosphate" (delta-5.1) first becomes detectable only at later stage of the activation and does coexist with pyrophosphate and triphosphate suggests that the pyridinium derivative of "metaphosphate" is most probably not directly formed from the hypothetical mixed anhydride or active "pseudourea" right at the beginning of the reaction of pdTac with TPS or DCC, but rather formed at later stage of the activation reaction from the degradation of the pyro- and triphosphates by the activating agent. The mixed anhydride or the active "pseudourea" is most possibly the active key intermediate.

Mechanism of interferon action--structural requirement of ligand and cellular specificity

We had reported the existence of 2'-5'P3A3 receptor on the peritoneal macrophages from Wistar rat. In this paper data are given to demonstrate that the ligand, for binding with 2'-5'P3A3 receptor and enhancing the phagocytosis of macrophages, must have a three-phosphate radical on its 5'-terminus and at least three adenylate residues in 2'-5'oligoadenylate. (3H)-2'-5'P3A3 can also bind on macrophages from other animals; and the binding of (3H)-2'-5'P3A3 on Hepatoma cell line 7402 is lower than that on macrophages; whereas it is very low (binding ratio less than 1%) on erythrocytes (from rabbit, rat and mouse) or human embryo lung fibroblast cells. The binding conditions of the ligand with 2'-5'P3A3 receptor have also been investigated.

Mechanism of interferon action--the discovery of the pppA2'p5'A2'p5'A receptor

In this paper it is demonstrated that (3H)2'-5'P3A3 can bind to the peritoneal macrophages from Wistar rat. This binding is strongly inhibited by cold 2'-5'P3A3, while the inhibiting capacity of 2'-5'P3I3 and 2'-5'A3 is very small, showing that this binding is highly specific. And the binding of (3H)2'-5'P3A3 is reversible, saturable and with high affinity. A Scatchard analysis of the binding data gives a linear plot, an apparent dissociation constant (Kd) about 1.3 X 10(-7) M and binding sites per cell about 2.1 X 10(7). The above evidence shows the existence of the 2'-5'P3A3 receptor, a fact which, to our knowledge, has not been reported before.

Mechanism of interferon action. Activation of macrophages and antagonism to alpha-feto-protein by pppA2'p5'A2'p5'A

pppA2'p5'A2'p5'A(2'-5'P3A3) activates macrophages and increases the phagocytosis of macrophages from different species including human beings. This indicates that the activation of macrophages may be a general action of 2'-5'P3A3. This discovery broadens the effect of 2'-5'P3A3 beyond the antiviral field. alpha-Feto-protein (AFP) inhibits the phagocytosis of macrophages and may be involved in the development of hepatoma. Data presented here show that 2'-5'P3A3 can antagonize this suppressive effect of AFP. Methods used so far for introducing 2'-5'P3A3 into the cells were made with the aid of CaCl2, etc. under conditions which may not be the same as those used clinically. It was found that 2'-5'P3A3 can develop its biological effect without the aid of CaCl2, etc.

Mechanism of interferon action III--significance of pppA2'p5'A2'p5'A in the antiviral action of interferon

This paper is to evidence that the antiviral effect of pppA2'P5'A2'P5'A(2'-5'P3A3) could cover a wide spectrum of viruses, the RNA viruses such as influenza H3N2/77, influenza H1N1/77, ECHO11, rhino, Sendai, Sindbis and VSV, and the DNA viruses such as herpes (type I). In addition, the antiviral effect of 2'-5'P3A3 on ECHO11 virus, as compared with other viruses, is more efficient than that of IFN. It seems likely that 2'-5'P3A3 plays an important role in the antiviral action of IFN. After comparing the action of 2'-5'P3A3 with interferon (IFN), it has appeared that the action of 2'-5'P3A3 is something parallel to that of IFN for most viruses. For a few viruses, however, considerable differences have been observed.

Synthesis of the 3'-half molecule of yeast alanine tRNA

This paper deals with the synthesis of the 3'-half molecule of yeast alanine transfer RNA (tRNAAlay) by ligation with T4 RNA ligase of three component oligonucleotide fragments corresponding to nucleotides 36-45(I), 46-57(II) and 58-76(III) in succession extending from the 3'-end to the 5'-end. First, in a ratio of acceptor to donor at 1.5 to 1, we adopted a method of three successive reactions, namely, the 5'-phosphorylation of the nonadecamer (III), ligation with the dodecamer (II) and the 5'-phosphorylation of the ligation product formed; with one isolation step and obtained the 5'-phosphorylated 31mer(46-76) (IV) in an overall yield of 70%. Then the 31mer(IV) as a donor was ligated with 3 times of decamer (I) to form the 41mer(36-76) (V), the 3'-half molecule of tRNAAlay. The yield was 67%. After 5'-phosphorylation, (V) was ligated with the natural 5'-half molecule to form the semi-synthetic tRNAAlay, which was biologically active, i.e. accepting and transferring (3H)-alanine into proteins.