摘要:

AbstractWe have studied the CD of both bacteriophage ϕ6 and ϕ6 nucleocapsid in order to assess thein situstate of the viral, double‐stranded RNA (dsRNA). The results showed that packaged ϕ6 RNA is slightly hyperdichroic (4–5%) at 264 nm relative to dsRNA in solution. Also, the CD of dsRNA within both the virus and the nucleocapsid was unlike CD spectra of any of the three types of dsRNA condensedin vitro, as described in the accompanying paper. Using a curve‐fitting program described elsewhere (Edmondson, S.P.&Gray, D.M. (1983)Nucleic Acids Res.11, 175–192), we have fit reference CD spectra of ϕ6 RNA and protein to measured CD spectra of ϕ6 intact phage and nucleocapsid. Results of the computer analysis indicated that ϕ6 RNAin situis spectrally similar to dsRNA that is slight

ISSN:0006-3525    

DOI:10.1002/bip.360250112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractOptically pure protectedL‐[3,4‐(1,4,7,10,13‐pentaoxatridecamethylene) phenyl] alanine, its dipeptide, diketopiperazine and homopolymer, protectedL‐[3,4‐(1,4,7,10,13,16‐hexaoxahexadecamethylene) phenyl] alanine and its polymer have been synthesized and characterized. These crown ether derivatives complex the potassium and ammonium cations as well as protonated leucine and glycine in tetrahydrofuran and methanol. They are also phase‐transfer agents. The cooperativity of the crown units was studied in detail for the di

ISSN:0006-3525    

DOI:10.1002/bip.360250113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractChanges in Δν½, the nmr linewidth of23Na, have been determined during titrations of helical DNA with polyamines (divalent putrescine and trivalent spermidine) and with inorganic cations (Mg2+and Co(NH3) 63+). In each case additions of a multivalent cation (Mz+) to a solution containing NaDNA and NaCl cause decreases in Δν½, which is a population‐weighted average of contributions from nuclei in bound and free environments. Thus, the binding of Mz+to DNA displaces sodium ions from regions where the quadrupolar relaxation of23Na is relatively efficient. At a given extent of titration, the binding of a polyamine produces a smaller decrease in Δν½than does the binding of an inorganic ion of the same valence. The concentration dependence of Δν½during the course of a titration can be interpreted most simply as a two‐state ion‐exchange reaction by assuming that the binding of Mzdoes not alterRB, the average relaxation rate of sodium nuclei that remain bound. On the basis of this assumption, the initial linear portions of titration curves can be analyzed to determine upper bounds forr°, the number of sodium ions bound per DNA phosphate in the absence of any competing counterion. Analyzing the titration curves for the four multivalent competitors leads to a range of upper‐bound estimates forr°: 0.5–0.8. The differences in these estimates could indicate that polyamines displace fewer sodium ions from DNA than do their smaller inorganic counterparts. Alternatively, the range in upper‐bound estimates forr° could also reflect specific differences in the effects of the various multivalent cations onRB, if this relaxation rate

ISSN:0006-3525    

DOI:10.1002/bip.360250114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360250101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY