The accumulation of Cd(II), Cu(II), Pb(II) and Zn(II) at mg L(-1) concentration levels by inactive freeze-dried biomass of Pseudomonas Putida has been investigated. These metals could be efficiently removed from diluted aqueous solutions. A contact time of 10 min was sufficient to reach equilibrium. The pH has a strong effect on metal biosorption and the optimal pH values were 6.0, 5.0-6.0, 6.0-6.5 and 7.0-7.5 for Cd(II), Cu(II), Pb(II) and Zn(II) respectively. Under these conditions there was 80% removal for all metals studied. The process of biosorption can be described by a Langmuir-type adsorption model. This model accounts for 98% of the data variance. The K(A) and q(max) parameters for each metal are strongly correlated (at confidence levels greater than 98%) with the metal acidity, quantified by the constant of the corresponding M(OH)(+) complex, thus confirming previous assertions by other authors.

The polypentapeptide of elastin, poly(VPGVG), has become an interesting model polypeptide in understanding the mechanism of protein folding and assembly. Due to its simple amino acid composition and the predominance of apolar side chains, this polymer shows strong hydrophobic-hydration phenomena. This paper explores, by calorimetric methods, the nature and structure of the clathrate-like arrangements that take place, surrounding the apolar side chains of the polymer. The performance of these methods, especially differential scanning calorimetry, has a well-gained reputation. In this work, the development of the clathrate-like structures around this model polymer has been followed from water deficiency to water-excess states. Two main conclusions have been obtained from the data obtained. First, there is an upper limit of about 170 water molecules per pentamer as the number of water molecules required to form all the possible clathrate-like structures. Second, these structures exist as an inhomogeneous population with energies spreading in a significantly broad range, which is likely related to differences in geometrical parameters (bond lengths and angles) of the clathrate structure.

The use of mobile technologies is reshaping how we teach and learn. In this paper we describe our research on the use of these technologies to teach physics. On the one hand we develop mobile applications to complement the traditional learning and to help students learn anytime and anywhere. The use of this applications has proved to have very positive influence on the students engagement. On the other hand, we use smartphones as measurement devices in physics experiments. This opens the possibility of designing and developing low cost laboratories where expensive material can be substituted by smartphones. The smartphones' sensors are reliable and accurate enough to permit good measurements. However, as it's shown with some examples, here special care must be taken if one doesn't know how these apps used to access the sensors' data are programmed.

SUMMARY: Poly(GVGVP) is the head of a novel group of biopolymers showing exceptional potential for future applications in different fields such as biomedical, environmental, energy or industrial. Taking into account their future development, further knowledge is needed to understand the molecular basis of their remarkable behaviour and other structural and technical parameters. This paper is devoted to a particular task of this challenge: the structural study of its solid state, which is approached for the first time in this work. Thermal, wide-angle X-ray diffraction and vibrational Raman analysis were used. On the whole, all the observations are consistent with the existence of a metastable amorphous phase composed by polymer chains without apparent conformational order. The main structural property is the existence of an extensive and dense net of hydrogen bonds, which seemed to comprise the majority of the amide groups present. Thermal treatment induces structural changes on this polymer. Part of the hydrogen bonds broke and the polymer chains reorganise to achieve a stable state. This state is non-crystalline in the classical sense and irreversible. Thus, due to the thermal input, the polymer chains had gained enough mobility to optimise their inter and intramolecular interactions and to fulfil their entropic requirements.

The polypentapeptide of elastin, poly(VPGVG), has become an interesting model polypeptide in understanding the mechanism of protein folding and assembly. Due to its simple amino acid composition and the predominance of apolar side chains, this polymer shows strong hydrophobic–hydration phenomena. This paper explores, by calorimetric methods, the nature and structure of the clathrate‐like arrangements that take place, surrounding the apolar side chains of the polymer. The performance of these methods, especially differential scanning calorimetry, has a well‐gained reputation. In this work, the development of the clathrate‐like structures around this model polymer has been followed from water deficiency to water‐excess states. Two main conclusions have been obtained from the data obtained. First, there is an upper limit of about 170 water molecules per pentamer as the number of water molecules required to form all the possible clathrate‐like structures. Second, these structures exist as an inhomogeneous population with energies spreading in a significantly broad range, which is likely related to differences in geometrical parameters (bond lengths and angles) of the clathrate structure.© 2000 John Wiley & Sons, Inc. Biopoly 54: 282–288, 2000