A single amino acid substitution alters ClpS2 binding specificity

ClpS2 is a small protein under development as a probe for selectively recognizing N-terminal amino acids of N-degron peptide fragments. To understand the structural basis of ClpS2 specificity for an N-terminal amino acid, all atom molecular dynamics (MD) simulations were conducted using the sequence of a bench-stable mutant of ClpS2, called PROSS. We predicted that a single amino acid leucine to asparagine substitution would switch the specificity of PROSS ClpS2 to an N-terminal tyrosine over the preferred phenylalanine. Experimental validation of the mutant using a fluorescent yeast-display assay showed an increase in tyrosine binding over phenylalanine, in support of the proposed hypothesis.     

Euler buckling-induced folding and rotation of red blood cells in an optical trap

We investigate the physics of an optically driven micromotor of biological origin. When a single, live red blood cell (RBC) is placed in an optical trap, the normal biconcave disc shape of the cell is observed to fold into a rod-like shape. If the trapping laser beam is circularly polarized, the folded RBC rotates. A model based on geometric considerations, using the concept of buckling instabilities, captures the folding phenomenon; the rotation of the cell is rationalized using the Poincaré sphere. Our model predicts that (i) at a critical power of the trapping laser beam the RBC shape undergoes large fluctuations, and (ii) the torque that is generated is proportional to the power of the laser beam. These predictions are verified experimentally. We suggest a possible mechanism for the emergence of birefringent properties in the RBC in the folded state.     

Survey ofLymantria obfuscata and its natural enemies in India

The status ofLymantria obfuscata Walker in India is discussed. Notes on its taxonomy, distribution, life-history and economic importance are given for comparison with those of the gypsy moth,Lymantria dispar (L.). Parasites ofL. obfuscata in India are reviewed. A survey in 1961–66 revealed an additional 50 species of natural enemies ofL. obfuscata in India. The incidence and biology of some of the important ones are presented. A comparison is made between these parasites and those ofL. dispar. Some of the natural enemies ofL. obfuscata already attackL. dispar in America. Others are closely related to the parasites of the gypsy moth. The scope for utilisation of parasites ofL. obfuscata in other countries is discussed. Possible use of parasites ofL. dispar from the U.S.A. or elsewhere againstL. obfuscata in India is suggested. Research financed in part by the U.S.D.A. under grant PL-480.     

Improvement of Ratio-Type Estimators

This paper proposes a method for using multi-auxiliary information at both the design and the estimation stages of a sample survey. The proposed method is an extension of the classical multivariate method of Olkin (1958). The results of Agarwal and Kumar (1978) come out as a special case.     

Tank treading of optically trapped red blood cells in shear flow

Tank-treading (TT) motion is established in optically trapped, live red blood cells (RBCs) held in shear flow and is systematically investigated under varying shear rates, temperature (affecting membrane viscosity), osmolarity (resulting in changes in RBC shape and cytoplasmic viscosity), and viscosity of the suspending medium. TT frequency is measured as a function of membrane and cytoplasmic viscosity, the former being four times more effective in altering TT frequency. TT frequency increases as membrane viscosity decreases, by as much as 10% over temperature changes of only 4°C at a shear rate of ∼43 s⁻¹. A threshold shear rate (1.5 ± 0.3 s⁻¹) is observed below which the TT frequency drops to zero. TT motion is also observed in shape-engineered (spherical) RBCs and those with cholesterol-depleted membranes. The TT threshold is less evident in both cases but the TT frequency increases in the latter cells. Our findings indicate that TT motion is pervasive even in folded and deformed erythrocytes, conditions that occur when such erythrocytes flow through narrow capillaries.     

A short account of the biological control ofPromecotheca cumingi [Col.: Hispidae] the coconut leaf-miner,in Sri Lanka

The leaf-mining hispidPromecotheca cumingi Baly, was first recorded as a pest on coconut in Sri lanka in October 1970. Its possible mode of entry and spread from the point of first occurrence are discussed. An account is given of the life-cycle, rate of multiplication, host plants and damage under Sri Lanka conditions. The spectacular success achieved in controlling the pest, which was spread over about 8,000 hectares, using the biological method, the techniques adopted for breeding and release of exotic parasites and the follow-up surveys to ascertain activity of the introduced parasites are discussed in detail. A brief account of the cost/benefit analysis is also given.     

Anomalies in the motion dynamics of long-flagella mutants of Chlamydomonas reinhardtii

Chlamydomonas reinhardtii has long been used as a model organism in studies of cell motility and flagellar dynamics. The motility of the well-conserved ‘9+2’ axoneme in its flagella remains a subject of immense curiosity. Using high-speed videography and morphological analyses, we have characterized long-flagella mutants (lf1, lf2-1, lf2-5, lf3-2, and lf4) of C. reinhardtii for biophysical parameters such as swimming velocities, waveforms, beat frequencies, and swimming trajectories. These mutants are aberrant in proteins involved in the regulation of flagellar length and bring about a phenotypic increase in this length. Our results reveal that the flagellar beat frequency and swimming velocity are negatively correlated with the length of the flagella. When compared to the wild-type, any increase in the flagellar length reduces both the swimming velocities (by 26–57%) and beat frequencies (by 8–16%). We demonstrate that with no apparent aberrations/ultrastructural deformities in the mutant axonemes, it is this increased length that has a critical role to play in the motion dynamics of C. reinhardtii cells, and, provided there are no significant changes in their flagellar proteome, any increase in this length compromises the swimming velocity either by reduction of the beat frequency or by an alteration in the waveform of the flagella.     

Coronary stenting using a 6 F. diagnostic catheter: a report of two cases

Standard guiding catheters for coronary interventions may not selectively engage the coronary ostium despite a successful cannulation with a diagnostic catheter of the same curve. This discrepancy is explained by a slight difference in shape between the two catheters (shorter tip of the guiding, absence of tip tapering, etc.). The authors report on the use of 6 F. coronary diagnostic catheters as guiding catheters for coronary angioplasty and stent implantation in two patients with critical stenoses: in the right coronary artery distal to a right internal mammary artery anastomosis in one and in the ostial right coronary artery in the other. In both cases, the use of diagnostic catheters was the key to success despite the vessel orifice being unfavourable for the use of different types of guiding catheters.