In this work with ab initio computations, we describe relevant interactions between protein active sites and ligands, using as a test case arthropod hemocyanins. A computational analysis of models corresponding to the oxygenated and deoxygenated forms of the hemocyanin active site is performed using the Density Functional Theory approach. We characterize the electron density distribution of the...

The eyes of the horseshoe crab Limulus polyphemus have long been used for studies of basic mechanisms of vision, and the structure and physiology of Limulus photoreceptors have been examined in detail. Less is known about the opsins Limulus photoreceptors express. We previously characterized a UV opsin (LpUVOps1) that is expressed in all three types of Limulus eyes (lateral compound eyes, media...

Pollution by metals may adversely affect organisms through the generation of reactive oxygen species (ROS). In this study, we examined the sublethal effects of two metals, copper and cadmium, on horseshoe crab (Limulus polyphemus) embryos. Exposure to copper or cadmium at concentrations of 0.01-10 mg/L for periods of 4, 8, 16 and 24 h had minimal effect on embryo survival except at 100 mg/L Cu....

The mediator of haemolysis in the plasma of the horseshoe crab, Limulus polyphemus, is limulin, a sialic acid-binding lectin. The haemolytic activity of limulin is inhibited by thiol ester-reacted forms of Limulus alpha(2)-macroglobulin, the third-most abundant protein of the plasma. Limulus alpha(2)-macroglobulin that has experienced cleavage of its internal thiol ester bond, consequent to rea...

The blue copper protein hemocyanin from the horseshoe crab Limulus polyphemus is among the largest respiratory proteins found in nature (3.5 MDa) and exhibits a highly cooperative oxygen binding. Its 48 subunits are arranged as eight hexamers (1x6mers) that form the native 8x6mer in a nested hierarchy of 2x6mers and 4x6mers. This quaternary structure is established by eight subunit types (terme...

Spontaneous, subthreshold fluctuations of membrane potential are recorded in the eccentric cell body or dendrite of the dark-adapted Limulus ommatidium. These slow potential fluctuations (SPF's) are random in amplitude and in time of occurrence. The relation between average frequency of SPF's and light intensity is linear for low light intensities and becomes a non-linear saturation for higher ...

The primary structure determination of the dimeric invertebrate alpha(2)-macroglobulin (alpha(2)M) from Limulus polyphemus has been completed by determining its sites of glycosylation and disulfide bridge pattern. Of seven potential glycosylation sites for N-linked glycosylation, six (Asn(275), Asn(307), Asn(866), Asn(896), Asn(1089), and Asn(1145)) carry common glucosamine-based carbohydrates ...

Restriction site variation in mitochondrial DNA (mtDNA) of the horseshoe crab (Limulus polyphemus) was surveyed in populations ranging from New Hampshire to the Gulf Coast of Florida. MtDNA clonal diversity was moderately high, particularly in southern samples, and a major genetic "break" (nucleotide sequence divergence approximately 2%) distinguished all sampled individuals which were north vs...

A limulus lysate assay was performed on cervical secretions from 66 women. When secretions were tested at a 1/100 dilution the assay gave a positive result in 15 (62.5%) of 24 patients with gonorrhoea confirmed by Gram-stained smear or culture or both. When secretions from seven of the nine remaining patients who had gonorrhoea but negative results to the limulus lysate test were retested at 1/...