The Coulomb energy and intrinsic dielectric polarizability (E,) of a series of doubly protonated gas-phase diaminoalkanes (+H3N(CH2),NH3+, n = 7-10, 12) are reported. The Coulomb energy is obtained from the difference in gas-phase basicity (GB) of the neutral monoamine, CH~(CH~),NHZ, and the apparent gas-phase basicity (GBaPP) of the corresponding 1,n-diaminoalkane (M + H)+ ion measured by proton transfer from (M + 2H)2+ ions to neutral reference molecules of known basicity. The distance between charges and the Coulomb energy as a function of n can be accurately calculated; comparison to experimentally measured values makes this an ideal system for evaluating the use of proton transfer reactivity for obtaining electrostatic forces in multiply protonated ions. The (M + 2H)2+ ion of 1,7-diaminoheptane, the smallest doubly protonated electrospray-generated ion ever reported, is found to have 32.0 kcal/mol of Coulomb energy; for the 1,12-diaminododecane, this value is 19.7 kcal/mol. From estimates of the distance between charges obtained by molecular modeling, we calculate an average cr of 1.01 f 0.07 for these diaminoalkanes. This value is significantly below the bulk solution dielectric constant of 1.9-2.0 for small n-alkanes. These results show that the ion conformation is linear and that shielding by (CH2)n between two charges in the gas phase is negligible. We find that cf does not significantly change with increasing distance between charges, providing experimental verification that the influence of a charge localized > 11 8, away from the reaction center can be fully accounted for by the combined effects of Coulomb repulsion and intrinsic reactivity of that center. IntroductionElectrospray ionization has become a powerful technique for producing protonated gas-phase ions directly from solution.'x2 For large molecules, multiple protonation occurs. This results in a distribution of molecular ions with d z ratios typically between 500 and 2500, from which molecular weights of large biomolecules can be determined with unprecedented (sub-ppm) ac~uracy.~ With increasing protonation, the contribution of Coulomb repulsion to ion zero-point energy increases, resulting in significantly greater ion reactivity and dissociation. Rates of proton transfer from protein ions to neutral bases increase with the number of charges due to the combined effects of increasing Coulomb repulsion and decreasing intrinsic basicity of charge site^.^-^ Effects of the Coulomb energy on proton transfer reactions were calculated by Bursey and Pederson* for diprotonated 1,3-diaminopropane. Barrier heights for bringing protonated ammonia and trimethylamine to within reaction distance of protonated 1,3-diaminopropane in a linear configuration were determined to be 33.1 and 34.5 kcal/mol, respectively. These values are 77% and 92% of a simple point charge model for a charge separation of 7.70 and 8.80 8, in these respective systems. Proton transfer reactions of the odd electron ion CmW2+ with neutral bases have been investigated by Bohme and co-w~...

Mechanisms underlying parent-offspring recognition in birds have fascinated researchers for centuries. Yet, the possibility that chicks recognise parental odour at hatching has been completely overlooked, despite the fact that olfaction is one of the first sensory modalities to develop, and social chemosignals occur in avian taxa. Here we show that Zebra Finch chicks (Taeniopygia guttata) are capable of identifying parental odours at hatching. In our first experiment, chicks begged significantly longer in response to the odour of their genetic mother or father compared to the odour of a non-relative of the same sex and reproductive status. In a second experiment, we cross-fostered eggs and tested the response of hatchlings to the scent of genetic vs. foster parents. Chicks from cross-fostered eggs responded significantly more to the odour of their genetic mother than their foster mother, but exhibited no difference in response to genetic vs. foster fathers. This is the first evidence that embryonic altricial birds are capable of acquiring chemosensory knowledge of their parents during early development, and retain chemical familiarity with their genetic mother despite egg cross-fostering. Furthermore our data reveals that kin recognition in birds can develop without any association with a genetic parent at hatching.

We describe an easy method to test odour detection and recognition in 1‐d‐old zebra finch hatchlings (Taeniopygia guttata). Day‐old chicks beg in a stereotypical posture, which can be induced by directing gentle puffs of air from a plastic wash bottle near the face. We used this method to experimentally test whether begging duration of chicks was indicative of nest odour recognition. We manipulated the olfactory environment of 12 nests throughout incubation and hatching with either an artificial odour (orange oil) or with a neutral control (tap water). We then presented these two stimulus odours to 25 day‐old chicks and measured the duration of the first begging bout exhibited for each odour. Zebra finches hatched in a nest environment enriched with orange oil scent begged significantly longer when exposed to orange oil odour, compared to control hatchlings. Our simple testing procedure can be used to efficiently quantify odour recognition and/or preference in altricial songbirds at a very early developmental stage.

Lactobacillus helveticus CNRZ 32: Attenuation and enzymatic properties for use as a secondary culture to produce cheese.

Visualisation aids in the evaluation of a 3-D data set, if a -perhaps imperfect -separability of different objects by their function value is assumed. An interpretation without explicit analysis can be carried out by reflection/transmission (RT) volume rendering where voxels, depending on their surface probability, reflect and transmit light. Colour coding voxels in RT rendering in order to attribute the surface to a specific object is not easy because the voxel value depends on the unknown objects meeting at the surface. This problem does not arise, if an emission/absorption (EA) method is applied. Emission and absorption of coloured light are associated with the probability of a voxel belonging to a certain object.We combined both approaches to exploit the RT renderer's ability to reveal surface details and the EA renderer's ability to differentiate objects. A user-defined operator decides whether a voxel belongs to the background, to a surface, or to an object. Background voxels are skipped. Object voxels contribute to accumulated light emission. Surface voxels reflect light from an outside light source. Colour is attributed only to object voxels, but it is possible to let coloured object voxels shine through semi-transparent surface voxels. CT sequences were visualised in order to display structures such as the ventricular system or areas of pathological processes. Although the differentiation of these structures was not complete, the display showed enough detail to convey the relevant shape to the user.