Cationic liposomes are known to be useful tools for gene transfection. However, the relation between transfection efficiency and physicochemical properties of liposomes has not been well understood. Here, we synthesized eight cationic derivatives of cholesterol which contain a tertiary amino head group with a different spacer arm. Transfection of plasmid pSVZCAT DNA into cells was done by cationic liposomes made of a mixture of dioleoylphosphatidylethanolamine (DOPE) and each cationic cholesterol derivative. At the same time we measured zeta potential of cationic liposomes by laser Doppler spectroscopy. The present results indicated that zeta potentials of cationic liposomes were well related to transfection activity of pSV2CAT DNA. This suggested that zeta potential of cationic liposomes is one of important factors which control gene transfection.
We have prepared monoclonal antibodies for the fluorescent molecular rotors 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ) and 9-(dicyanovinyl)julolidine (DCVJ). Mouse monoclonal antibody (IgG2b) prepared against CCVJ-conjugated bovine serum albumin strongly bound CCVJ and DCVJ. The CCVJ (or DCVJ) binding to IgG and Fab was accompanied by a drastic increase in fluorescence quantum yield, suggesting the restriction of intramolecular rotational relaxation about the donor-acceptor bond of the fluorophores. Nonspecific IgG never changed the quantum yield of the fluorophores. From the Scatchard plots, the association constants of CCVJ to IgG and Fab were 6.8 x 10(7) and 5.4 x 10(7) M-1, respectively, and the numbers of moles of CCVJ bound per mole of IgG and Fab were calculated to be 2.0 (+/- 0.1) and 1.0 (+/- 0.05), respectively. The fluorescence spectra of the IgG-bound CCVJ were quite similar to those of Fab-bound CCVJ. The fluorescence lifetimes of the IgG-bound and Fab-bound CCVJ were 388 and 383 ps at 25 degrees C, respectively. They were 6.3 times as long as the fluorescence lifetime of CCVJ free in solution (62 ps). These results indicated that the drastic increases in quantum yields were due to the decreases of the nonradiative rate constants of the antibody-bound CCVJ, as well as due to the changes of the intrinsic radiative rate constant, and that the nonradiative internal rotations about the donor-acceptor bond of CCVJ were not dependent on the size of the bound antibody molecules.(ABSTRACT TRUNCATED AT 250 WORDS)
The antitumor activity of various platinum(II) complexes of 1,2-cyclohexanediamine and 2-(aminomethyl)cyclohexylamine isomers against leukemia P388 was evaluated by means of the platinum analogue study protocol recommended by the National Cancer Institute. For the former complexes, trans isomers are more efficacious than the corresponding cis isomers. For the latter complexes, cis isomers seem to be somewhat more active than trans isomers. 2-(Aminomethyl)cyclohexylamine platinum complexes exhibited higher activity than 1,2-cyclohexanediamine complexes in this tumor system. These findings encouraged us to determine the structural differences between 1,2-cyclohexanediamine and 2-(aminomethyl)cyclohexylamine complexes. Their structures of platinum complexes were elucidated from circular dichroism and 13C NMR spectral analyses, and it has been concluded that the cyclohexane ring of cis-1,2-cyclohexanediamine is nearly perpendicular to the chelate ring, while both rings of trans-1,2-cyclohexanediamine and trans-2-(aminomethyl)cyclohexylamine complexes lie in a common plane. The structure of cis-2-(aminomethyl)cyclohexylamine complexes is flexible, and the cyclohexane ring is not perpendicular to the chelate ring. The coplanarity of trans isomers and the flexibility of cis-2-(aminomethyl)cyclohexylamine complexes allow them easy approach to the target DNA. However, the perpendicular ring of cis-1,2-cyclohexanediamine complexes would prevent their interactions with dna molecules due to the steric hindrance.
There is an increasing demand from both patients and practicing oncologists for orally formulated chemotherapy. The present study focused on the oral formulation for natural products that may be effectively used in oncologic treatment regimens. Tumor-bearing mice treated with intratumoral administration of aqueous ammonium oxalate-soluble and ethanol-insoluble derivatives of Agaricus blazei showed marked tumor regression at doses ranging from 0.1 to 2.5 mg (p < 0.05 vs. saline control; n = 7). However, oral administration of this same fraction, either prior to, simultaneously with, or after, tumor cell inoculation did not result in tumor regression (p > 0.05 vs. control). When this fraction was treated with hydrochloric acid (acid-treated fraction; ATF), intratumoral administration resulted in a marked regression of tumor growth comparable to that of the acid-untreated fraction. More importantly, parenteral administration of ATF resulted in a significantly greater regression of tumor growth than that produced by the untreated fraction (p < 0.05 vs. untreated; n = 7). When a total of 4.5 mg of ATF was given orally at varying schedules prior to, simultaneously with, or after, tumor inoculation, a significant regression was seen using a schedule starting 4 days prior to inoculation (p < 0.05 vs. all other treatments; n = 7). NMR and molecular analyses showed that the ATF fraction had a molecular weight of approximately 10 kDa and consisted mainly of only (1,6)-beta- D-polyglucose. These results suggest that the oral administration of simple acid-treated ATF results in a remarkable tumor regression. Thus, simple acid hydrolysis of natural products may not only bring measurable benefits in oncological practice, but may also be a useful general formulation for natural products for oral chemotherapy.
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