'Smart' polymers and what they could do in biotechnology and medicine.

Stimulus-responsive or 'smart' polymers undergo strong conformational changes when only small changes in the environment (e. g. pH, temperature, ionic strength) occur. These changes result in phase separation from aqueous solution or order-of-magnitude changes in hydrogel size. Smart polymers are used in bioseparation and drug delivery, for the development of new biocatalysts, as biomimetic actuators, and as surfaces with switchable hydrophobic-hydrophilic properties.     

Algal ecotypes: what they are and what they are not

A salt tolerant ecotype of Scenedesmus armatus from the Baltic Sea is reported. Salinity treatments also reveal variable plasticity of several morphological features of this alga The problem of drawing a sharp distinction between stable and plastic attributes is discussed and it is concluded that the terms ecotype and ecophene, as originally defined, are no longer applicable to algae. A redefinition of the ecotype is proposed.     

How to obtain labeled proteins and what to do with them

We review new and established methods for the chemical modification of proteins in living cells and highlight recent applications. The review focuses on tag-mediated protein labeling methods, such as the tetracysteine tag and SNAP-tag, and new developments in this field such as intracellular labeling with lipoic acid ligase. Recent promising advances in the incorporation of unnatural amino acids into proteins are also briefly discussed. We describe new tools using tag-mediated labeling methods including the super-resolution microscopy of tagged proteins, the study of the interactions of proteins and protein domains, the subcellular targeting of synthetic ion sensors, and the generation of new semisynthetic metabolite sensors. We conclude with a view on necessary future developments, with one example being the selective labeling of non-tagged, native proteins in complex protein mixtures.     

Understanding the cytochrome bc complexes by what they don't do. The Q-cycle at 30

The cytochrome (cyt) bc(1), b(6)f and related complexes are central components of the respiratory and photosynthetic electron transport chains. These complexes carry out an extraordinary sequence of electron and proton transfer reactions that conserve redox energy in the form of a trans-membrane proton motive force for use in synthesizing ATP and other processes. Thirty years ago, Peter Mitchell proposed a general turnover mechanism for these complexes, which he called the Q-cycle. Since that time, many opposing schemes have challenged the Q-cycle but, with the accumulation of large amounts of biochemical, kinetic, thermodynamic and high-resolution structural data, the Q-cycle has triumphed as the accepted model, although some of the intermediate steps are poorly understood and still controversial. One of the major research questions concerning the cyt bc(1) and b(6)f complexes is how these enzymes suppress deleterious and dissipative side reactions. In particular, most Q-cycle models involve reactive semiquinone radical intermediates that can reduce O(2) to superoxide and lead to cellular oxidative stress. Current models to explain the avoidance of side reactions involve unprecedented or unusual enzyme mechanisms, the testing of which will involve new theoretical and experimental approaches.     

How tumors escape immune destruction and what we can do about it

There is strong circumstantial evidence that tumor progression in cancer patients is controlled by the immune system. As will be detailed below, this conclusion is based on observations that tumor progression is often associated with secretion of immune suppressive factors and/or downregulation of MHC class I antigen presentation functions. The inference is that tumors must have elaborated strategies to circumvent an apparently effective immune response. Importantly, a tumor-specific immune response cannot be detected in most individuals. While this failure is in part technical, it also suggests that the magnitude of the immune responses to which tumors have to respond is low. This raises the concern, which is the underlying theme of this commentary, that a more robust immune response elicited by deliberate vaccination will exacerbate the rate of immune escape and nullify the potential benefits of immune-based therapies. Received: 20 March 1999 / Accepted: 3 May 1999     

How to have an effective academic sabbatical: recommendations for what to do and what to avoid

Sabbaticals - i.e., academic sabbaticals, sabbatical leaves, sabbatical semesters - provide faculty members with a unique opportunity to engage in scholarly projects. Ranging from a year to shorter periods, these time windows - usually free of rigid day-to-day obligations - can be powerful means to reflect on past and present projects, to renew perspectives, and to receive fresh impetus for both your research and teaching. When reading the literature on sabbaticals, it is somewhat surprising that relatively small amounts of space are devoted to this important part of academic life. Here we provide practical recommendations [1-4: pre-sabbatical; 5-8: intra-sabbatical; 9-10: post-sabbatical] for making your sabbatical a satisfying endeavor.     

Maternal effects in Daphnia: what mothers are telling their offspring and do they listen?

Maternal effects can significantly impact offspring performance. Provisioning of offspring with energy stores can quantitatively alter their growth rates, survivorship, and future fecundity, and influence population regulatory mechanisms. In this paper, we show that maternal effects can also qualitatively affect offspring reproduction (i.e. their mode of reproduction). The freshwater herbivore Daphnia pulex can change the amount of energy allocated between asexual and ephippial egg production. Our experiments on individuals, experiencing “step‐up” or “step‐down” food manipulations, reveal that offspring qualitatively shift their energy allocation away from asexual reproduction to ephippial egg production when there is a simple mismatch between maternal and offspring food environments. We show that the response is asymmetric with respect to changes in food level, ephippial egg production is higher with a greater mismatch between environments, and that the effect can be observed in dynamic experimental populations. These results point to a “generational memory” that could challenge our interpretation of field patterns and mechanisms influencing population dynamics in Daphnia–algal systems.     

Chimpanzees know what conspecifics do and do not see

We report a series of experiments on social problem solving in chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual were put into competition over two pieces of food. In all experiments dominants obtained virtually all of the foods to which they had good visual and physical access. However, subordinates were successful quite often in three situations in which they had better visual access to the food than the dominant, for example, when the food was positioned so that only the subordinate (and not the dominant) could see it. In some cases, the subordinate might have been monitoring the behaviour of the dominant directly and simply avoided the food that the dominant was moving towards (which just happened to be the one it could see). In other cases, however, we ruled out this possibility by giving subordinates a small headstart and forcing them to make their choice (to go to the food that both competitors could see, or the food that only they could see) before the dominant was released into the area. Together with other recent studies, the present investigation suggests that chimpanzees know what conspecifics can and cannot see, and, furthermore, that they use this knowledge to devise effective social-cognitive strategies in naturally occurring food competition situations. Copyright 2000 The Association for the Study of Animal Behaviour.