Recombinant antibodies often contain N-terminal mutations arising from the use of degenerate cloning primer sets and/or the introduction of restriction sites in the framework 1 regions. We studied the effects of such mutations in a recombinant anti-estradiol Fab fragment derived from the hybridoma cell line 57-2. The 5′ ends of the heavy and light chain genes were originally modified to introduce the restriction sites XhoI and SacI, respectively, for cloning purposes. However, the affinity and specificity of the recombinant Fab were lowered compared to the proteolytic Fab′ fragment of the parental hybridoma IgG. Replacing the mutated sites with authentic amino acid coding sequences restored the binding properties as well as increased the bacterial production levels fivefold and 10-fold at 30 and 37 °C, respectively. Local changes in the antigen binding site were probed by determining the affinity constants (Ka) for estradiol and four related steroids. It was found that the mutated heavy chain amino terminus specifically increased the Ka for testosterone whereas the mutated light chain amino terminus decreased the Ka for all of the steroids to the same extent; the heavy and light chain effects were additive. Analysis of a newly determined crystal structure of the authentic Fab 57-2 in complex with estradiol suggests that mutations in the residue 2 in VH, and 2 and 4 in the VL domain were those responsible for the observed effects. Their general roles as structure-determining residues for the CDR3 loops imply that similar effects can occur with other recombinant antibodies as well.

In the past decade or so, the universal dominance of l- over d-amino acids in living organisms has been questioned. This interesting and wide-ranging book summarizes the current state of knowledge on the occurrence, biosynthesis, and roles of d-amino acid containing peptides, with a strong emphasis on those in multicellular organisms. The opening chapter by Scaloni et al. provides a practical guide to the detection and analysis of d-amino acids. The subsequent four chapters describe studies related to the presence of d-amino acids in antimicrobial and opioid peptides in frogs, molluscan neuropeptides, and crustacean hyperglycemic hormones. Although the work could have been summarized more succinctly and there is, as is common with this type of text, some overlap between the chapters, the inclusion of experimental details will be of interest to the specialist.

Oleg Ptitsyn was a pioneer in protein folding studies: his discovery of molten globule folding intermediates revolutionized the field. He died in England on March 22, 1999, after a heart attack. Oleg Ptitsyn was born in St. Petersburg (Leningrad) on July 18, 1929, and took his M.Sc. in Molecular Physics at the University of Leningrad at the age of 22. He remained in Leningrad, at the Institute of High Molecular Compounds, first taking his Ph.D. in 1954 and then his D.Sc. in 1963 in physical and mathematical sciences. In 1967, he became Deputy Director of the Institute of Protein Research and simultaneously Head of the Laboratory of Protein Physics at Pushchino, at the Academy of Sciences Institute for Protein Research. He retained his position at Pushchino after becoming in 1992 a visiting member of the NIH Laboratory of Mathematical Biology, in the section of Robert Jernigan.