Chemoselective Installation of Amine Bonds on Proteins through Aza-Michael Ligation

Chemical modification of proteins is essential for a variety of important diagnostic and therapeutic applications. Many strategies developed to date lack chemo- and regioselectivity as well as result in non-native linkages that may suffer from instability in vivo and adversely affect the protein's structure and function. We describe here the reaction of N-nucleophiles with the amino acid dehydroalanine (Dha) in a protein context. When Dha is chemically installed in proteins, the addition of a wide-range N-nucleophiles enables the rapid formation of amine linkages (secondary and tertiary) in a chemoselective manner under mild, biocompatible conditions. These new linkages are stable at a wide range of pH values (pH 2.8 to 12.8), under reducing conditions (biological thiols such as glutathione) and in human plasma. This method is demonstrated for three proteins and is shown to be fully compatible with disulfide bridges, as evidenced by the selective modification of recombinant albumin that displays 17 structurally relevant disulfides. The practicability and utility of our approach is further demonstrated by the construction of a chemically modified C2A domain of Synaptotagmin-I protein that retains its ability to preferentially bind to apoptotic cells at a level comparable to the native protein. Importantly, the method was useful for building a homogeneous antibody-drug conjugate with a precise drug-to-antibody ratio of 2. The kinase inhibitor crizotinib was directly conjugated to Dha through its piperidine motif, and its antibody-mediated intracellular delivery results in 10-fold improvement of its cancer cell-killing efficacy. The simplicity and exquisite site-selectivity of the aza-Michael ligation described herein allows the construction of stable secondary and tertiary amine-linked protein conjugates without affecting the structure and function of biologically relevant proteins.

A Comprehensive Methodology for Assessing Human-Robot Team Performance for Use in Training and Simulation

New methodologies and quantitative measurements for evaluating human-robot team performance must be developed to achieve effective coordination between teams of humans and unmanned vehicles. The Mixed Initiative Team Performance Assessment System (MITPAS) provides such a comprehensive measurement methodology. MITPAS consists of a methodology, tools and procedures to measure the performance of mixed manned and unmanned teams in both training and real world operational environments. This paper describes MITPAS and the results of an initial experiment conducted to validate the measures and gain insight into the effect of robot competence on operator trust as well as on human-robot team performance.

Motivational factors in vigilance: effects of instructions on performance in a complex vigilance task

Pre-task instructions have been a neglected source of motivation in vigilance. In the present study, 32 Ss monitored a complex visual vigilance display for 40 min. with a signal rate of 60/hr. 16 Ss were told that such tasks are usually challenging (positive set) and 16 were told such tasks are usually monotonous (negative set). Performance was significantly better throughout the session by Ss with the positive set and decrements did not occur with either group. The results indicate the importance of motivational factors in vigilance. Implications for vigilance research are discussed.