Notes on the Tax Treatment of Structures

More than three quarters of the United States tangible capital stock represents structures. Tax policies potentially have a major impact on both the level and composition of investment in structures and equipment. This point is explicitly recognized in most discussions of the effects of capital income taxation. Two aspects of the taxation of structures --the relative burden placed on structures as opposed to equipment investment and the non-taxation of owner occupied housing under the income tax -- have attracted substantial attention in recent years. This paper explores these two aspects of the taxation of structures investments. While the tax system may well have a potent impact on the level and composition of structures investment, this paper argues that conventional analyses of these effects are very misleading. We reach two main conclusions. First,under current tax law, certain types of structures investment are very highly tax favored. Structures can be transferred and therefore depreciated more than once, and structures may be readily financed with tax-favored debt. Overall, itis unlikely that a significant bias towards equipment and against structures exists under current law. Second, the conventional view that the tax system is biased in favor of homeownership is wrong. Because of the possibility of "tax arbitrage" between high bracket landlords and low bracket tenants, the tax system has long favored rental over ownership for most households. The 1981 reforms by reducing the top marginal tax rate reduced this bias somewhat.

Combining uretdione and disulfide reversibly degradable polyurethanes : route to alternating block copolymers

Uretdione (temperature and catalyst controlled) and disulphide (REDOX controlled) functionalised polyurethanes have been described and the reversibility of these bonds tested. The polymers have been synthesised with reversible covalent groups present throughout their backbone, developing routes to reversibly degradable polyurethanes. These materials degrade and reheal in response to different external stimuli, which supplies a proof of concept for controlling the molecular weight, and therefore, the physical properties of a polyurethane. Further, a unique route to an alternating block copolymer is also discussed that utilises a mixture of disulphide and uretdione functionalised polymers as the reagents to form a thiourethane. The dramatically reduced safety hazards of dealing with the functionalised polymers, in comparison to the free isocyanate and thiols, could be of great interest to industrial application for current drives towards safer routes to polyurethanes

Relaxin family peptide receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Relaxin family peptide receptors (RXFP, nomenclature as agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [18, 75]) may be divided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are heterodimeric peptide hormones structurally related to insulin: relaxin-1, relaxin, relaxin-3 (also known as INSL7), insulin-like peptide 3 (INSL3) and INSL5. Species homologues of relaxin have distinct pharmacology and relaxin interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [172]. relaxin-3 is the ligand for RXFP3 but it also binds to RXFP1 and RXFP4 and has differential affinity for RXFP2 between species [170]. INSL5 is the ligand for RXFP4 but is a weak antagonist of RXFP3. relaxin and INSL3 have multiple complex binding interactions with RXFP1 [176] and RXFP2 [84] which direct the N-terminal LDLa modules of the receptors together with a linker domain to act as a tethered ligand to direct receptor signaling [173]. INSL5 and relaxin-3 interact with their receptors using distinct residues in their B-chains for binding, and activation, respectively [211, 97]

Relaxin family peptide receptors in GtoPdb v.2021.3

Relaxin family peptide receptors (RXFP, nomenclature as agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [18, 81]) may be divided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are heterodimeric peptide hormones structurally related to insulin: relaxin-1, relaxin, relaxin-3 (also known as INSL7), insulin-like peptide 3 (INSL3) and INSL5. Species homologues of relaxin have distinct pharmacology and relaxin interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [184]. relaxin-3 is the ligand for RXFP3 but it also binds to RXFP1 and RXFP4 and has differential affinity for RXFP2 between species [183]. INSL5 is the ligand for RXFP4 but is a weak antagonist of RXFP3. relaxin and INSL3 have multiple complex binding interactions with RXFP1 [189] and RXFP2 [91] which direct the N-terminal LDLa modules of the receptors together with a linker domain to act as a tethered ligand to direct receptor signaling [186]. INSL5 and relaxin-3 interact with their receptors using distinct residues in their B-chains for binding, and activation, respectively [225, 104]

Relaxin family peptide receptors in GtoPdb v.2023.1

Relaxin family peptide receptors (RXFP, nomenclature as agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [23, 119]) may be divided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are heterodimeric peptide hormones structurally related to insulin: relaxin-1, relaxin, relaxin-3 (also known as INSL7), insulin-like peptide 3 (INSL3) and INSL5. Species homologues of relaxin have distinct pharmacology and relaxin interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [260]. relaxin-3 is the ligand for RXFP3 but it also binds to RXFP1 and RXFP4 and has differential affinity for RXFP2 between species [259]. INSL5 is the ligand for RXFP4 but is a weak antagonist of RXFP3. relaxin and INSL3 have multiple complex binding interactions with RXFP1 [267] and RXFP2 [132] which direct the N-terminal LDLa modules of the receptors together with a linker domain to act as a tethered ligand to direct receptor signaling [262]. INSL5 and relaxin-3 interact with their receptors using distinct residues in their B-chains for binding, and activation, respectively [321, 152]

Differential Roles for Disulfide Bonds in the Structural Integrity and Biological Activity of κ-Bungarotoxin, a Neuronal Nicotinic Acetylcholine Receptor Antagonist †

ABSTRACT: κ-Bungarotoxin, a κ-neurotoxin derived from the venom of the banded Krait, Bungarus multicinctus, is a homodimeric protein composed of subunits of 66 amino acid residues containing five disulfide bonds. κ-Bungarotoxin is a potent, selective, and slowly reversible antagonist of R3 2 neuronal nicotinic acetylcholine receptors. κ-Bungarotoxin is structurally related to the R-neurotoxins, such as R-bungarotoxin derived from the same snake, which are monomeric in solution and which effectively antagonize muscle type receptors (R1 1γδ) and the homopentameric neuronal type receptors (R7, R8, and R9). Like the κ-neurotoxins, the long R-neurotoxins contain the same five conserved disulfide bonds, while the short R-neurotoxins only contain four of the five. Systematic removal of single disulfide bonds in κ-bungarotoxin by site-specific mutagenesis reveals a differential role for each of the disulfide bonds. Removal of either of the two disulfides connecting elements of the carboxy terminal loop of this toxin (Cys 46-Cys 58 and Cys 59-Cys 64) interferes with the ability of the toxin to fold. In contrast, removal of each of the other three disulfides does not interfere with the general folding of the toxin and yields molecules with biological activity. In fact, when either C3-C21 or C14-C42 are removed individually, no loss in biological activity is seen. However, removing both produces a polypeptide chain which fails to fold properly. Removal of the C27-C31 disulfide only reduces the activity of the toxin 46.6-fold. This disulfide may play a role in specific interaction of the toxin with specific neuronal receptors. The R-and κ-neurotoxins, isolated from the venoms of snakes from the elapid and hydrophid families, are effective antagonists of nicotinic acetylcholine receptors (1). While the R-neurotoxins effectively antagonize muscle type receptors (R1 1γδ) and the homopentameric neuronal type receptors (R7, R8, and R9), the κ-neurotoxins are potent, selective antagonists of R3 2 (and to a lesser extent R4 2) neuronal nicotinic receptors (2). The binding to these receptors is characterized by very slow kinetic off rates for both classes of toxin. It has also been reported that κ-bungarotoxin is capable of inhibiting receptors containing R2 2, R2 4, R3 4, R4 4, and even R1 1γδ combinations expressed in frog oocytes when the toxin is coapplied with agonist (3). In this case, however, the kinetics of inhibition is characterized by very fast off rates. The reason for these differences in kinetic behavior is currently unknown. In addition to their characteristic interactions with receptors, the R-and κ-neurotoxins also display distinctive structural characteristics. Prominent among these is the observation that the R-neurotoxins are monomeric in solution while the κ-neurotoxins are dimeric in solution. The dimerization of κ-bungarotoxin has been shown to result from specific residues which are conserved in the κ-neurotoxins but not the R-neurotoxins that interact at a dimer interface formed by the two strands of the third loop of each subunit (4). The dimeric nature of the κ-neurotoxins may play a role in their binding to receptors and may account at least in part for their different specificity and kinetic characteristics (5). These neurotoxins can also be classified as either short or long neurotoxins based on conserved elements of structure. Short neurotoxins contain 60-62 amino acid residues and four disulfide bridges in common positions. Long neurotoxins usually consist of 66-74 amino acid residues and have a fifth disulfide bond in addition to the four found in short neurotoxins. Short and long neurotoxins are also distinguished by conserved sequence deletions and additions relative to one another (1). Both short and long neurotoxins, including κ-neurotoxins, have been studied extensively by site-directed mutagenesis (6-9), but there have been few reports regarding the function or role of the conserved disulfide bonds. Do these bonds simply play a structural role in stabilizing the conformation