It is known that the occurrence of kinks in the acyl chains impede close packing of the lipids and thereby retain the membrane fluidity at lower temperature . Such kinks are provided by the presence of cyclopropane rings or C=C double bonds in the acyl chains. The key focus is to reveal which sort of kinks are more rigid to disrupt the packing or more precisely the ordering of the lipid bilayer. We have considered the three types of acyl chains (cyclopropane ring-, monounsaturated chain-, and saturated chain-containing), as taken in the calculation of <SCD>. The kink angle is calculated using the vectors shown in Figure . The kink angle distributions, presented in Figure for various temperatures, show that the kink of a cyclopropane containing acyl chain in NM is not perturbed by the cold shock. They also do not allow other saturated and monounsaturated fatty acid chains to align themselves in an ordered arrangement. On the other hand, in both MMU and MMS, the kink angle sharply increases below a certain temperature for the saturated and monounsaturated chains. The higher kink rigidity of the cyclopropane containing fatty acid chain introduces the packing defects which in turn hinder the gel phase formation. The presence of cyclopropane rings not only inhibit the phase transition of the LCFAs, but also avert the same for the LSFAs and LUFAs in the NM system. Therefore, the cyclopropane rings are more effective than C=C double bonds to prevent the phase transition of the lipids from fluid to gel phase at lower temperature Apart from kink angle, dihedral angle distributions are also relevant to provide an overall understanding about the stability of various structural conformations of the lipid acyl chains. The highest peak of the distribution specifies the most probable conformation. Since in realistic bacterial membranes -cis conformations are most abundant, in the present study, only -cis geometry of the double bond or cyclopropane (CP) rings are considered. The CP rings or double bonds are located nearly in the mid position of the acyl chains for the three membrane systems. For each acyl chain, we have calculated the distributions of dihedral angles: 𝜑 9 , 𝜑 10 , and 𝜑 11 at three representative temperatures: 250, 310, and 350 K (Figure ). For both cyclopropane and C=C containing chains a sharp peak is observed at 0 o (𝜑 10 ). The -cis geometry forces the C8 and C11 carbons to stay at 0 o for both the chains. The C9 and C10 carbons are sp 2 hybridized for the monounsaturated chains. Hence, straightening of the chains at lower temperature (250 K) promotes high strain on the C=C double bond. Similar effect is observed for the cyclopropane ring system also. Here, although the C9 and C10 carbons of the CP rings are sp 3 hybridized, the highly strained ring structure does not facilitate the twisting of the C-C single bonds (C8, C9 and C10, C11), which in turn gives rise to a sharp peak at 0 o . For the monounsaturated chains we observe two minor peaks at 120 o for the 𝜑 9 and 𝜑 11 dihedrals.