Confidence as an expression of commitment: why misplaced expressions of confidence backfire

Because communication can be abused by senders, it is not inherently stable. One way of stabilizing communication is for senders to commit to their messages. If a sender is committed to a message, she is willing to incur a cost (direct or reputational) if the message is found to be unreliable. This cost provides a reason for receivers to accept messages to which senders are committed. We suggest that expressions of confidence can be used as commitment signals: messages expressed more confidently commit their senders more. On this basis, we make three predictions: that confidently expressed messages are more persuasive (H1’, already well established), that senders whose messages were accepted due to the senders' confidence but were then found to be unreliable should incur costs (H2’), and that if a message is accepted for reasons other than confidence, when it is found to be unreliable the sender should incur lower reputational costs than if the message had been accepted on the basis of the sender's confidence (H3’). A review of the literature revealed broadly supportive but still ambiguous evidence for H2’ and no tests of H3’. In experiments 1, 2, and 3 (testing H2’) participants received the same advice from two senders, one being confident and the other unconfident. Participants were more likely to follow the advice of the confident sender, but once the advice was revealed to have been misguided, participants adjusted their trust so that they trusted the initially unconfident sender more than the confident sender. In experiments 3 and 4 (testing H3’) participants chose between either two senders differing in confidence or two senders differing in competence. Participants followed the advice of the confident sender and of the competent sender. When it was revealed that the advice was misguided, the confident sender suffered from a larger drop in trust than the competent sender. These results are relevant for communicative theories of overconfidence.     

Fluorescence properties of reduced thionicotinamide--adenine dinucleotide and of its complex with octopine dehydrogenase.

Reduced 3-thionicotinamide--adenine dinucleotide (sNADH) is shown to be fluorescent, with an emission maximum at 510 nm when excited in the region of the absorption maximum (398 nm), and with a very low quantum yield, (3.4 +/- 0.5) x 10(-4). The interaction between sNADH and octopine dehydrogenase was investigated by ultraviolet-difference spectroscopy and fluorescence. Some surprising fluorescence features were found when sNADH was bound to the enzyme in the presence of D-octopine, as follows. (a) There is an unusually high enhancement of the dinucleotide fluorescence (by at least a factor of 100) attended by a 40-nm blue shift of the emission maximum. (b) The protein fluorescence is quenched almost completely. (c) The bound coenzyme analog undergoes a photoreaction, which proceeds differently from that occurring the free form. These features appear to be unique to the octopine.sNADH complex, as for example they are not present when sNADH is bound to horse liver alcohol dehydrogenase, or when NADH is bound to octopine dehydrogenase. The possible origin of these fluorescence features is discussed. Binding and kinetic studies were carried out with sNAD and sNADH. It was found that sNAD neither binds nor acts kinetically as a coenzyme. sNADH exhibits relatively good binding, with Km and Ki values close to those of the natural coenzyme, but the turnover number is 460 times smaller than that with NADH. The kinetic consequences of these findings are discussed. The sNADH dissociation constants were determined as a function of temperature, and appear to be practically temperature-independent in the range 10--40 degrees C. It seems thus, in agreement with previous studies, that the interaction between octopine dehydrogenase and coenzymes proceeds athermically, regardless of the structure, affinity, and chemical reactivity of the coenzyme. The possible biological and chemical meaning of this finding is discussed.     

“山水林田湖草沙生命共同体”耦合框架、模型与展望

“山水林田湖草沙生命共同体”系统保护与修复是我国生态文明建设的重要内容。明确生命共同体的耦合机制，是科学地进行生态保护和修复工作的关键。针对当前生命共同体耦合机制不清、理论和方法不健全的问题，从耦合的视角出发，在小流域尺度上单一生态系统内部生态要素的耦合、流域尺度上不同生态系统之间的耦合、区域尺度上人与自然的耦合三个方面进行整合，在此基础上探讨了多尺度山水林田湖草沙耦合理论，提出了一般性的山水林田湖草沙耦合理论框架。梳理并比较了当前主要的生态系统模型、景观模型、统计学模型以及复合生态系统的多模型耦合方法，综合提出了一个适用于"山水林田湖草沙生命共同体"耦合研究方法。对进一步完善山水林田湖草沙一体化保护修复提出了建议，包括：一是构建多源信息数据库，推进定量化耦合机制研究；二是开展全生命周期监测与评估，探索适应性治理路径；三是强化多元主体参与，完善协同保护机制。     

Reactions of nucleic acid bases with alpha-acetylenic esters. Synthesis and enzymatic evaluation of chemically modified nucleotides

Analogues of adenine nucleotides, containing an additional chloromethyl-pyrimidone ring fused to the purine base, were obtained by treatment of AMP, ADP and ATP with an alpha-acetylenic ester, methyl 4-chlorobut-2-ynoate. These compounds were tested for their ability to substitute for the natural substrates or cofactors of several enzymes. With the ADP analogue, pyruvate kinase showed a significant increase of the Km value and a moderate decrease of V, while the reverse was observed when hexokinase was tested with modified ATP. Adenylate kinase was active with the ATP analogue but not with the AMP derivative. Myosin accepted the ATP analogue as a substrate, but was irreversibly modified. Among the dehydrogenases tested, only glucose-6-phosphate dehydrogenase was inhibited by the nucleotide analogue. The structure--activity relationship of these nucleotide derivatives, which represent the largest dimensional deviation known from natural nucleotides, is discussed in comparison with some earlier described dimensional probes of enzyme-nucleotide binding sites.     

Intra- and interspecific variation in the chitin content of some anostracans

Chitin was assayed in adults of nine anostracan species (Streptocephalus dichotomus, S. proboscideus, S. simplex, S. torvicornis, Thamnocephalus platyurus, Dendrocephalus brasiliensis, Chirocephalus diaphanus, Artemia salina and Branchipus schaefferi) using a highly specific enzymatic method. Cysts of A. salina, T. platyurus and larvae of A. salina and S. simplex were also analysed for their chitin content. The results demonstrated a weak interspecific variation in chitin content among the adults. On the whole, it ranged from 9 to 33 mg chitin (g dry mass)⁻¹. In most species, the chitin level was not significantly different between males and females. In contrast, chitin levels varied significantly between cysts, larvae and adults within species. Comparison of the chitin content of anostracans revealed a comparable or lower chitin level than other crustaceans. This revised version was published online in August 2006 with corrections to the Cover Date.