Numerous long-standing questions in origins-of-life research center on the history of biopolymers. For example, how and why did nature select the polypeptide backbone and proteinaceous side chains? Depsipeptides, containing both ester and amide linkages, have been proposed as ancestors of polypeptides. In this paper, we investigate cationic depsipeptides that form under mild dry-down reactions. We compare the oligomerization of various cationic amino acids, including the cationic proteinaceous amino acids (lysine, Lys; arginine, Arg; and histidine, His), along with nonproteinaceous analogs of Lys harboring fewer methylene groups in their side chains. These analogs, which have been discussed as potential prebiotic alternatives to Lys, are ornithine, 2,4-diaminobutyric acid, and 2,3-diaminopropionic acid (Orn, Dab, and Dpr). We observe that the proteinaceous amino acids condense more extensively than these nonproteinaceous amino acids. Orn and Dab readily cyclize into lactams, while Dab and Dpr condense less efficiently. Furthermore, the proteinaceous amino acids exhibit more selective oligomerization through their α-amines relative to their side-chain groups. This selectivity results in predominantly linear depsipeptides in which the amino acids are α-amine−linked, analogous to today’s proteins. These results suggest a chemical basis for the selection of Lys, Arg, and His over other cationic amino acids for incorporation into proto-proteins on the early Earth. Given that electrostatics are key elements of protein−RNA and protein−DNA interactions in extant life, we hypothesize that cationic side chains incorporated into proto-peptides, as reported in this study, served in a variety of functions with ancestral nucleic acid polymers in the early stages of life.

The close synergy between peptides and nucleic acids in current biology is suggestive of a functional co-evolution between the two polymers. Here we show that cationic proto-peptides (depsipeptides and polyesters), either produced as mixtures from plausibly prebiotic dry-down reactions or synthetically prepared in pure form, can engage in direct interactions with RNA resulting in mutual stabilization. Cationic proto-peptides significantly increase the thermal stability of folded RNA structures. In turn, RNA increases the lifetime of a depsipeptide by >30-fold. Proto-peptides containing the proteinaceous amino acids Lys, Arg, or His adjacent to backbone ester bonds generally promote RNA duplex thermal stability to a greater magnitude than do analogous sequences containing non-proteinaceous residues. Our findings support a model in which tightly-intertwined biological dependencies of RNA and protein reflect a long co-evolutionary history that began with rudimentary, mutually-stabilizing interactions at early stages of polypeptide and nucleic acid co-existence.

Fifty-one cases of solitary rectal ulcer syndrome diagnosed over the past 10 years have been studied. The syndrome, of which solitary ulceration was a feature in only 35 per cent of cases, included patients with multiple 'solitary' ulcers (22 per cent), broad-based polypoid lesions (25 per cent) and patchy granular hyperaemic rectal mucosa (18 per cent). The syndrome was found to be strongly associated with abnormal rectal descent. Full-thickness prolapse to or beyond the anal verge was present in 59 per cent of patients while a further 32 per cent had lesser degrees of rectal descent. In only 9 per cent was no such abnormality demonstrated. Treatment with high roughage diet supplemented with bulking agents benefited two-thirds of 27 patients so treated. Ivalon sponge rectopexy has been performed in 6 patients with associated complete rectal prolapse, and in the first 3 of these (followed for a sufficient period) the results have been satisfactory.

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S ome isolated observations have been made from time to time upon the temperatures of the Monotremes.# More recently S utherland'!' has published an important series of observations upon the temperatures of Echidna and several Marsupials, and upon the variation in their body-temperature with changes in that of the air. These observations of S utherland have been referred to in some detail by V ernon,j in whose paper, and in P embrey's chapter " On Animal-heat " in S chafer's ' Text-hook of Physiology,' and in P ichet's article " Chaleur " in the ' Dictionnaire de Physiologie,' the literature of the subject is so fully collected that it will merely he necessary for me to refer to those papers directly bearing upon the present work, when discussing the experimental results.Without doubt, as pointed out by S utherland, § Monotremes and Marsupials present a stage of physiological development intermediate between the fairly accurate homoeothermism of the higher mammals, and the rudimentary indications in this direction which, according to V ernon,|| occur in lower vertebrates, but the conclusion of both Sutherland and V ernon that O" is nearly a animal," which conclusion is based upon some observations of Macleay's,1F is very far from being sustained by my experiments.The present paper is an attempt to locate more precisely the position of * Miklouho-Macleay, ' Linn.

Computer Science Education should not drive a wedge between the social and the technical, but rather link both through ihe formal and informal curriculum" [5]."Societal and technical aspects of computing are interdependent Technical issues are best understood (and most effectively tau^t) in their sodal context, and ihe societal aspects of computing are best understood in ffie context of the underlying technical detail. Far from detracting from the students' learning of technical itformation, including societal aspects in the computer science curriculum can enhance students' teaming, increase their motivation, and deepen their understanding" [10]. AND KEITH MILLER HERE IS A GROV^^NG AWARENESS THAT ETHICAL PRACTICE AND social responsibility are becoming increasingly important aspects of the computing profession. This is demonstrated by the publication of a number of recent articles in Communications related to tiiese topics [2, 4, 5, 8, 13-15]. It is also demonstrated in the most recent revision to the computer science curriculum, Computing Curricula 1991 [1], which stated, "Undergraduate programs should provide an environment in which students are exposed to the ethical and societal issues associated with the computing field. This includes maintaining currency with recent technological and theoretical developments, upholding general professional standards, and coMMumenTioNB or THB neai Ücccmbcr I99(i/Vol. 39, No. 12 D<.-cC-.nl,fl llíyÜ/V.ji, XI. No. iL> COMMUHICariONE THE ACM CHUCK HUFF (huff®stolaf.edu) is an associate professor of p.sychology at St. Olaf College, DONALD GOTTERBARN (gotterba@seasva.gwu.edti) is an associate professor in tlie Comptiter and Information Sciences ) is an associate professor of computer science at tlie University of Illinois at Springfield.

How to prepare tomorrow's professionals for questions that can't always be answered with faster, better, or more technology.

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