Isolation of two odorant-binding proteins from mouse nasal tissue.

1. Two soluble proteins, with good affinity to tritiated 2-isobutyl-3-methoxypyrazine, have been purified from mouse nasal mucosa. 2. The first protein is a heterodimer with subunits of apparent M(r) 18 and 19 kDa and isoelectric point of 4.9; the second is a monomer of M(r) 21 kDa and isoelectric point of 4.8. 3. The characteristics of these binding proteins are compared with those of the other known OBPs and urinary proteins and their putative role is discussed.     

2-Aminopurine Fluorescence: Discrimination Between Specific and Unspecific Ligand Binding to the Kissing-Loop Dimer of the HIV-1 RNA

Abstract

The fluorescent 2-aminopurine probe (2-AP) incorporated into the loop of 23-mer RNA hairpin of HIV-1 genome dimerization initiation site (DIS) was used for discrimination of specific and unspecific binding of paromomycin and spermine to the kissing loop dimer (KD) formed in solution. While both ligands stabilized the KD RNA structure, only paromomycin binding resulted in significant increase of 2-AP fluorescence. These observations suggest that the 2-AP fluorescent RNA construct might be useful for selecting ligands specifically binding the HIV-1 kissing loop RNA dimer.     

Synthesis of thiazole and selenazole derivatives with affinity for the odorant-binding protein.

Three new ligands for odorant-binding proteins (OBPs) have been prepared, to be used in protein structure studies: the photoaffinity label 2-azido-4-butyl-5-propylthiazole, the NMR probe 2-trifluoromethyl-4-butyl-5-propylthiazole and the X-ray probe 2-amino-4-butyl-5-propylselenazole. All three compounds bind the bovine OBP with dissociation constants in the micromolar range.     

On the stability of delay equation models of simple human stretch reflexes

Human stretch reflexes (SRs) are often too weak and ineffectual to provide adequate postural regulation or rhythmic movement boosting (e.g. in ankle pushoff at the end of stance phase in fast running). Recent improvements in methods of artificially enhancing skeletomotor responses, especially in therapeutic regimens, should not be widely employed until the clonus-resisting stability properties of SRs are better understood. We formulate an idealized linear servo model of a segmentally-mediated SR system which includes the often ignored electromechanical coupling delay. For typical closed-loop (delay/gain) ratios, the model is shown to be unstable for all values of loop gain when operating as a position servo, but maximally stable when operating as a velocity servo. We claim that the velocity servo or more of its nonlinear relatives is a better model for some well studied SRs than, e.g., Houk's stiff muscle hypothesis. We also present evidence that even feeble and quickly saturating monosynaptic postural servos are always unstable if operated as pure position regulators.     

Chondrostoma polylepis Steindachner X Rutilus lemmingii (Steindachner) (Osteichthyes, Cyprinidae), a new natural hybrid from the Duero River basin, Spain

Hybrids of the Iberian nase, Chondrostoma polylepis, and the pardilla roach, Rutilus lemmingii, were found in the River Yeltes, Salamanca, Spain. Morphological multivariate (PCA) and univariate (ANOVA) analyses of 10 C. polylepis, 33 R. lemmingii and 15 hybrids have shown that the hybrids are intermediate in shape between the parent species, with a stronger resemblance to the nase. A brief discussion of the potential causes of the hybridization is presented.