Alteration of the Route to Menaquinone towards Isochorismate-Derived Metabolites

Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg–Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L⁻¹). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway.     

The Role of SSL in Cybersecutiry

In this paper, the security in computer networks using the secure sockets layer (SSL) protocol is discussed. Security refers to many different ideas, principles, and concepts. SSL provides three categories of security: confidentiality, message integrity, and endpoint authentication. It's important to keep security traits in mind as we consider some common scenarios involving secure sockets layer (SSL). The SSL can help secure communications in e-commerce and in other business or personal communication where security is required between a client and server. However, SSL doesn't address some other security aspects     

An evaluation of early or delayed adjuvant chemotherapy in premenopausal patients with advanced breast cancer undergoing oophorectomy

We treated randomly 75 premenopausal patients with advanced breast cancer with combination chemotherapy (5-fluorouracil, cyclophosphamide and prednisone), either as an early adjunct to oophorectomy or as a delayed treatment upon appearance of progressive metastatic disease after operation. The group receiving early systemic chemotherapy enjoyed an improved response rate, an improved survival rate and, most importantly, an improved progression-free interval (median of 53 versus 17 weeks). With the exclusion of the group with early (within three weeks after oophorectomy) progression, the progression-free intervals had a median duration of 77 weeks in the early-treatment group versus 33 weeks in the control group. The early-progression group did exceedingly poorly, although systemic chemotherapy was employed at that juncture, having a median survival of 22 weeks as compared to 144 weeks in the immediate-treatment group and 105 weeks in the control group.