793 research outputs found
Heme binding by the N-terminal fragment 1-44 of human growth hormone
No full textFragment 1-44 of human growth hormone (hGH), prepared in vitro by limited proteolysis of the hormone with pepsin at low pH, encompasses in full the N-terminal helix of this four-helix bundle protein [Spolaore, B., Polverino de Laureto, P., Zambonin, M., and Fontana, A. (2004) Biochemistry 40, 9460-9468]. Here, we report the new and interesting observation that fragment 1-44 can bind heme. The binding property is specific for the N-terminal helix of hGH, since heme binding does not occur with fragment 45-191 or the entire protein. The spectral characteristics of Fe-protoporphyrin IX are those of a low-spin, hexacoordinated iron ligated by two imidazole rings of His residues or His and Met residues. Far-UV circular dichroism (CD) measurements revealed that fragment 1-44 acquires a helical secondary structure upon heme binding. Heme appears to be bound to the fragment in a stereospecific way, since an induced dichroic signal is observed in the Soret region of the CD spectrum. The heme-fragment complex occurs in a 1:1 molar ratio, as determined by spectrophotometric titration, as well as by electrospray-ionization mass spectrometric analysis of the complex. The fragment alone is much more susceptible to tryptic digestion than the heme complex, implying a more folded and rigid structure of this last species. It is proposed that the molecular features of fragment 1-44 determining its heme-binding property reside in the amphipathic character of the helix adopted by the fragment, as well as in the presence in its polypeptide chain of His18, His21, and Met14. These residues can act as specific ligands for the heme-iron, as observed with cytochromes
Letter by Brocco et al regarding article, "Percutaneous treatment with drug-eluting stent implantation versus bypass surgery for unprotected left main stenosis: A single-center experience"
No full textThe number and size of nations revisited: Endogenous border formation with non-uniform population distributions
No full textThe endogenous border formation model of Alesina and Spolaore (1997) has received a lot of attention in the economics community. One of its central messages is that in a democratic world in equilibrium there is an ineciently large number of nation states. However, this result is obtained under very specic assumptions like a uniform population distribution and no population mobility. In this paper, I generalize the model of Alesina and Spolaore allowing for population distributions other than the uniform distribution. Since this generalization is accompanied by the loss of tractability in closed form, I calculate the equilibria by means of numerical computation. It turns out that the above-mentioned central result is highly sensitive to the choice of population distribution and that the model shows four different regimes depending on the chosen distribution. Furthermore, the behaviour implied by the Alesina and Spolaore model with uniform population distribution is the exception, not the rule.Size of Nations; Endogenous Border Formation; Computational Economics
Unexpected effects of coffee consumption on liver enzymes.
No full textThe effects of regular daily coffee consumption on liver enzymes were studied in a large number of subjects from the general population. In coffee drinkers, liver enzymes (gamma-glutamyl transferase, alanine-amino transferase, and alkaline phosphatase) and serum bilirubin were lower than in non-coffee-drinking subjects or in those consuming less than 3 cups daily. The hypothesis proposed is that liver enzymes are a target for caffeine contained in coffee
[The reduction of respiratory function is an independent risk factor in the elderly].
No full textUn'analisi dello studio CASTEL
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